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 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package javax.crypto;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.regex.*;


import java.security.*;
import java.security.Provider.Service;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;

import javax.crypto.spec.*;

import java.nio.ByteBuffer;
import java.nio.ReadOnlyBufferException;

import sun.security.util.Debug;
import sun.security.jca.*;

This class provides the functionality of a cryptographic cipher for
encryption and decryption. It forms the core of the Java Cryptographic
Extension (JCE) framework.
In order to create a Cipher object, the application calls the
Cipher's getInstance method, and passes the name of the
requested transformation to it. Optionally, the name of a provider
may be specified.
A transformation is a string that describes the operation (or
set of operations) to be performed on the given input, to produce some
output. A transformation always includes the name of a cryptographic
algorithm (e.g., AES), and may be followed by a feedback mode and
padding scheme.
 A transformation is of the form:


"algorithm/mode/padding" or

"algorithm"

 (in the latter case,
provider-specific default values for the mode and padding scheme are used).
For example, the following is a valid transformation:

    Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");

Using modes such as CFB and OFB, block ciphers can encrypt data in units smaller than the cipher's actual block size. When requesting such a mode, you may optionally specify the number of bits to be processed at a time by appending this number to the mode name as shown in the "AES/CFB8/NoPadding" and "AES/OFB32/PKCS5Padding" transformations. If no such number is specified, a provider-specific default is used. Thus, block ciphers can be turned into byte-oriented stream ciphers by using an 8 bit mode such as CFB8 or OFB8. 
Author:
Jan Luehe
See Also:
KeyGenerator
SecretKey
Since:
1.4/**
 * This class provides the functionality of a cryptographic cipher for
 * encryption and decryption. It forms the core of the Java Cryptographic
 * Extension (JCE) framework.
 *
 * <p>In order to create a Cipher object, the application calls the
 * Cipher's <code>getInstance</code> method, and passes the name of the
 * requested <i>transformation</i> to it. Optionally, the name of a provider
 * may be specified.
 *
 * <p>A <i>transformation</i> is a string that describes the operation (or
 * set of operations) to be performed on the given input, to produce some
 * output. A transformation always includes the name of a cryptographic
 * algorithm (e.g., <i>AES</i>), and may be followed by a feedback mode and
 * padding scheme.
 *
 * <p> A transformation is of the form:<p>
 *
 * <ul>
 * <li>"<i>algorithm/mode/padding</i>" or
 * <p>
 * <li>"<i>algorithm</i>"
 * </ul>
 *
 * <P> (in the latter case,
 * provider-specific default values for the mode and padding scheme are used).
 * For example, the following is a valid transformation:<p>
 *
 * <pre>
 *     Cipher c = Cipher.getInstance("<i>AES/CBC/PKCS5Padding</i>");
 * </pre>
 *
 * Using modes such as <code>CFB</code> and <code>OFB<code>, block
 * ciphers can encrypt data in units smaller than the cipher's actual
 * block size.  When requesting such a mode, you may optionally specify
 * the number of bits to be processed at a time by appending this number
 * to the mode name as shown in the "{@code AES/CFB8/NoPadding}" and
 * "{@code AES/OFB32/PKCS5Padding}" transformations. If no such
 * number is specified, a provider-specific default is used.
 * Thus, block ciphers can be turned into byte-oriented stream ciphers by
 * using an 8 bit mode such as CFB8 or OFB8.
 *
 * @author Jan Luehe
 * @see KeyGenerator
 * @see SecretKey
 * @since 1.4
 */

public class Cipher {

    private static final Debug debug =
                        Debug.getInstance("jca", "Cipher");

    
Constant used to initialize cipher to encryption mode.
/**
     * Constant used to initialize cipher to encryption mode.
     */
    public static final int ENCRYPT_MODE = 1;

    
Constant used to initialize cipher to decryption mode.
/**
     * Constant used to initialize cipher to decryption mode.
     */
    public static final int DECRYPT_MODE = 2;

    
Constant used to initialize cipher to key-wrapping mode.
/**
     * Constant used to initialize cipher to key-wrapping mode.
     */
    public static final int WRAP_MODE = 3;

    
Constant used to initialize cipher to key-unwrapping mode.
/**
     * Constant used to initialize cipher to key-unwrapping mode.
     */
    public static final int UNWRAP_MODE = 4;

    
Constant used to indicate the to-be-unwrapped key is a "public key".
/**
     * Constant used to indicate the to-be-unwrapped key is a "public key".
     */
    public static final int PUBLIC_KEY = 1;

    
Constant used to indicate the to-be-unwrapped key is a "private key".
/**
     * Constant used to indicate the to-be-unwrapped key is a "private key".
     */
    public static final int PRIVATE_KEY = 2;

    
Constant used to indicate the to-be-unwrapped key is a "secret key".
/**
     * Constant used to indicate the to-be-unwrapped key is a "secret key".
     */
    public static final int SECRET_KEY = 3;

    // The provider
    private Provider provider;

    // The provider implementation (delegate)
    private CipherSpi spi;

    // The transformation
    private String transformation;

    // Crypto permission representing the maximum allowable cryptographic
    // strength that this Cipher object can be used for. (The cryptographic
    // strength is a function of the keysize and algorithm parameters encoded
    // in the crypto permission.)
    private CryptoPermission cryptoPerm;

    // The exemption mechanism that needs to be enforced
    private ExemptionMechanism exmech;

    // Flag which indicates whether or not this cipher has been initialized
    private boolean initialized = false;

    // The operation mode - store the operation mode after the
    // cipher has been initialized.
    private int opmode = 0;

    // The OID for the KeyUsage extension in an X.509 v3 certificate
    private static final String KEY_USAGE_EXTENSION_OID = "2.5.29.15";

    // next SPI  to try in provider selection
    // null once provider is selected
    private CipherSpi firstSpi;

    // next service to try in provider selection
    // null once provider is selected
    private Service firstService;

    // remaining services to try in provider selection
    // null once provider is selected
    private Iterator<Service> serviceIterator;

    // list of transform Strings to lookup in the provider
    private List<Transform> transforms;

    private final Object lock;

    
Creates a Cipher object.
Params:
cipherSpi – the delegate
provider – the provider
transformation – the transformation/**
     * Creates a Cipher object.
     *
     * @param cipherSpi the delegate
     * @param provider the provider
     * @param transformation the transformation
     */
    protected Cipher(CipherSpi cipherSpi,
                     Provider provider,
                     String transformation) {
        // See bug 4341369 & 4334690 for more info.
        // If the caller is trusted, then okey.
        // Otherwise throw a NullPointerException.
        if (!JceSecurityManager.INSTANCE.isCallerTrusted()) {
            throw new NullPointerException();
        }
        this.spi = cipherSpi;
        this.provider = provider;
        this.transformation = transformation;
        this.cryptoPerm = CryptoAllPermission.INSTANCE;
        this.lock = null;
    }

    
Creates a Cipher object. Called internally and by NullCipher.
Params:
cipherSpi – the delegate
transformation – the transformation/**
     * Creates a Cipher object. Called internally and by NullCipher.
     *
     * @param cipherSpi the delegate
     * @param transformation the transformation
     */
    Cipher(CipherSpi cipherSpi, String transformation) {
        this.spi = cipherSpi;
        this.transformation = transformation;
        this.cryptoPerm = CryptoAllPermission.INSTANCE;
        this.lock = null;
    }

    private Cipher(CipherSpi firstSpi, Service firstService,
            Iterator<Service> serviceIterator, String transformation,
            List<Transform> transforms) {
        this.firstSpi = firstSpi;
        this.firstService = firstService;
        this.serviceIterator = serviceIterator;
        this.transforms = transforms;
        this.transformation = transformation;
        this.lock = new Object();
    }

    private static String[] tokenizeTransformation(String transformation)
            throws NoSuchAlgorithmException {
        if (transformation == null) {
            throw new NoSuchAlgorithmException("No transformation given");
        }
        /*
         * array containing the components of a Cipher transformation:
         *
         * index 0: algorithm component (e.g., AES)
         * index 1: feedback component (e.g., CFB)
         * index 2: padding component (e.g., PKCS5Padding)
         */
        String[] parts = new String[3];
        int count = 0;
        StringTokenizer parser = new StringTokenizer(transformation, "/");
        try {
            while (parser.hasMoreTokens() && count < 3) {
                parts[count++] = parser.nextToken().trim();
            }
            if (count == 0 || count == 2 || parser.hasMoreTokens()) {
                throw new NoSuchAlgorithmException("Invalid transformation"
                                               + " format:" +
                                               transformation);
            }
        } catch (NoSuchElementException e) {
            throw new NoSuchAlgorithmException("Invalid transformation " +
                                           "format:" + transformation);
        }
        if ((parts[0] == null) || (parts[0].length() == 0)) {
            throw new NoSuchAlgorithmException("Invalid transformation:" +
                                   "algorithm not specified-"
                                   + transformation);
        }
        return parts;
    }

    // Provider attribute name for supported chaining mode
    private final static String ATTR_MODE = "SupportedModes";
    // Provider attribute name for supported padding names
    private final static String ATTR_PAD  = "SupportedPaddings";

    // constants indicating whether the provider supports
    // a given mode or padding
    private final static int S_NO    = 0;       // does not support
    private final static int S_MAYBE = 1;       // unable to determine
    private final static int S_YES   = 2;       // does support

    
Nested class to deal with modes and paddings.
/**
     * Nested class to deal with modes and paddings.
     */
    private static class Transform {
        // transform string to lookup in the provider
        final String transform;
        // the mode/padding suffix in upper case. for example, if the algorithm
        // to lookup is "AES/CBC/PKCS5Padding" suffix is "/CBC/PKCS5PADDING"
        // if lookup is "AES", suffix is the empty string
        // needed because aliases prevent straight transform.equals()
        final String suffix;
        // value to pass to setMode() or null if no such call required
        final String mode;
        // value to pass to setPadding() or null if no such call required
        final String pad;
        Transform(String alg, String suffix, String mode, String pad) {
            this.transform = alg + suffix;
            this.suffix = suffix.toUpperCase(Locale.ENGLISH);
            this.mode = mode;
            this.pad = pad;
        }
        // set mode and padding for the given SPI
        void setModePadding(CipherSpi spi) throws NoSuchAlgorithmException,
                NoSuchPaddingException {
            if (mode != null) {
                spi.engineSetMode(mode);
            }
            if (pad != null) {
                spi.engineSetPadding(pad);
            }
        }
        // check whether the given services supports the mode and
        // padding described by this Transform
        int supportsModePadding(Service s) {
            int smode = supportsMode(s);
            if (smode == S_NO) {
                return smode;
            }
            int spad = supportsPadding(s);
            // our constants are defined so that Math.min() is a tri-valued AND
            return Math.min(smode, spad);
        }

        // separate methods for mode and padding
        // called directly by Cipher only to throw the correct exception
        int supportsMode(Service s) {
            return supports(s, ATTR_MODE, mode);
        }
        int supportsPadding(Service s) {
            return supports(s, ATTR_PAD, pad);
        }

        private static int supports(Service s, String attrName, String value) {
            if (value == null) {
                return S_YES;
            }
            String regexp = s.getAttribute(attrName);
            if (regexp == null) {
                return S_MAYBE;
            }
            return matches(regexp, value) ? S_YES : S_NO;
        }

        // ConcurrentMap<String,Pattern> for previously compiled patterns
        private final static ConcurrentMap<String, Pattern> patternCache =
            new ConcurrentHashMap<String, Pattern>();

        private static boolean matches(String regexp, String str) {
            Pattern pattern = patternCache.get(regexp);
            if (pattern == null) {
                pattern = Pattern.compile(regexp);
                patternCache.putIfAbsent(regexp, pattern);
            }
            return pattern.matcher(str.toUpperCase(Locale.ENGLISH)).matches();
        }

    }

    private static List<Transform> getTransforms(String transformation)
            throws NoSuchAlgorithmException {
        String[] parts = tokenizeTransformation(transformation);

        String alg = parts[0];
        String mode = parts[1];
        String pad = parts[2];
        if ((mode != null) && (mode.length() == 0)) {
            mode = null;
        }
        if ((pad != null) && (pad.length() == 0)) {
            pad = null;
        }

        if ((mode == null) && (pad == null)) {
            // AES
            Transform tr = new Transform(alg, "", null, null);
            return Collections.singletonList(tr);
        } else { // if ((mode != null) && (pad != null)) {
            // AES/CBC/PKCS5Padding
            List<Transform> list = new ArrayList<Transform>(4);
            list.add(new Transform(alg, "/" + mode + "/" + pad, null, null));
            list.add(new Transform(alg, "/" + mode, null, pad));
            list.add(new Transform(alg, "//" + pad, mode, null));
            list.add(new Transform(alg, "", mode, pad));
            return list;
        }
    }

    // get the transform matching the specified service
    private static Transform getTransform(Service s,
                                          List<Transform> transforms) {
        String alg = s.getAlgorithm().toUpperCase(Locale.ENGLISH);
        for (Transform tr : transforms) {
            if (alg.endsWith(tr.suffix)) {
                return tr;
            }
        }
        return null;
    }

    
Returns a Cipher object that implements the specified
transformation.
 This method traverses the list of registered security Providers,
starting with the most preferred Provider.
A new Cipher object encapsulating the
CipherSpi implementation from the first
Provider that supports the specified algorithm is returned.
 Note that the list of registered providers may be retrieved via the Security.getProviders() method. 
Params:
transformation – the name of the transformation, e.g.,
AES/CBC/PKCS5Padding.
See Appendix A in the

Java Cryptography Architecture Reference Guide
for information about standard transformation names.
Throws:
NoSuchAlgorithmException – if transformation
         is null, empty, in an invalid format,
         or if no Provider supports a CipherSpi implementation for the
         specified algorithm.
NoSuchPaddingException – if transformation
         contains a padding scheme that is not available.
See Also:
Provider
Returns:
a cipher that implements the requested transformation./**
     * Returns a <code>Cipher</code> object that implements the specified
     * transformation.
     *
     * <p> This method traverses the list of registered security Providers,
     * starting with the most preferred Provider.
     * A new Cipher object encapsulating the
     * CipherSpi implementation from the first
     * Provider that supports the specified algorithm is returned.
     *
     * <p> Note that the list of registered providers may be retrieved via
     * the {@link Security#getProviders() Security.getProviders()} method.
     *
     * @param transformation the name of the transformation, e.g.,
     * <i>AES/CBC/PKCS5Padding</i>.
     * See Appendix A in the
     * <a href=
     *   "{@docRoot}/../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture Reference Guide</a>
     * for information about standard transformation names.
     *
     * @return a cipher that implements the requested transformation.
     *
     * @exception NoSuchAlgorithmException if <code>transformation</code>
     *          is null, empty, in an invalid format,
     *          or if no Provider supports a CipherSpi implementation for the
     *          specified algorithm.
     *
     * @exception NoSuchPaddingException if <code>transformation</code>
     *          contains a padding scheme that is not available.
     *
     * @see java.security.Provider
     */
    public static final Cipher getInstance(String transformation)
            throws NoSuchAlgorithmException, NoSuchPaddingException
    {
        List<Transform> transforms = getTransforms(transformation);
        List<ServiceId> cipherServices = new ArrayList<ServiceId>(transforms.size());
        for (Transform transform : transforms) {
            cipherServices.add(new ServiceId("Cipher", transform.transform));
        }
        List<Service> services = GetInstance.getServices(cipherServices);
        // make sure there is at least one service from a signed provider
        // and that it can use the specified mode and padding
        Iterator<Service> t = services.iterator();
        Exception failure = null;
        while (t.hasNext()) {
            Service s = t.next();
            if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                continue;
            }
            Transform tr = getTransform(s, transforms);
            if (tr == null) {
                // should never happen
                continue;
            }
            int canuse = tr.supportsModePadding(s);
            if (canuse == S_NO) {
                // does not support mode or padding we need, ignore
                continue;
            }
            if (canuse == S_YES) {
                return new Cipher(null, s, t, transformation, transforms);
            } else { // S_MAYBE, try out if it works
                try {
                    CipherSpi spi = (CipherSpi)s.newInstance(null);
                    tr.setModePadding(spi);
                    return new Cipher(spi, s, t, transformation, transforms);
                } catch (Exception e) {
                    failure = e;
                }
            }
        }
        throw new NoSuchAlgorithmException
            ("Cannot find any provider supporting " + transformation, failure);
    }

    
Returns a Cipher object that implements the specified
transformation.
 A new Cipher object encapsulating the
CipherSpi implementation from the specified provider
is returned.  The specified provider must be registered
in the security provider list.
 Note that the list of registered providers may be retrieved via the Security.getProviders() method. 
Params:
transformation – the name of the transformation,
e.g., AES/CBC/PKCS5Padding.
See Appendix A in the

Java Cryptography Architecture Reference Guide
for information about standard transformation names.
provider – the name of the provider.
Throws:
NoSuchAlgorithmException – if transformation
         is null, empty, in an invalid format,
         or if a CipherSpi implementation for the specified algorithm
         is not available from the specified provider.
NoSuchProviderException – if the specified provider is not
         registered in the security provider list.
NoSuchPaddingException – if transformation
         contains a padding scheme that is not available.
IllegalArgumentException – if the provider
         is null or empty.
See Also:
Provider
Returns:
a cipher that implements the requested transformation./**
     * Returns a <code>Cipher</code> object that implements the specified
     * transformation.
     *
     * <p> A new Cipher object encapsulating the
     * CipherSpi implementation from the specified provider
     * is returned.  The specified provider must be registered
     * in the security provider list.
     *
     * <p> Note that the list of registered providers may be retrieved via
     * the {@link Security#getProviders() Security.getProviders()} method.
     *
     * @param transformation the name of the transformation,
     * e.g., <i>AES/CBC/PKCS5Padding</i>.
     * See Appendix A in the
     * <a href=
     *   "{@docRoot}/../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture Reference Guide</a>
     * for information about standard transformation names.
     *
     * @param provider the name of the provider.
     *
     * @return a cipher that implements the requested transformation.
     *
     * @exception NoSuchAlgorithmException if <code>transformation</code>
     *          is null, empty, in an invalid format,
     *          or if a CipherSpi implementation for the specified algorithm
     *          is not available from the specified provider.
     *
     * @exception NoSuchProviderException if the specified provider is not
     *          registered in the security provider list.
     *
     * @exception NoSuchPaddingException if <code>transformation</code>
     *          contains a padding scheme that is not available.
     *
     * @exception IllegalArgumentException if the <code>provider</code>
     *          is null or empty.
     *
     * @see java.security.Provider
     */
    public static final Cipher getInstance(String transformation,
                                           String provider)
            throws NoSuchAlgorithmException, NoSuchProviderException,
            NoSuchPaddingException
    {
        if ((provider == null) || (provider.length() == 0)) {
            throw new IllegalArgumentException("Missing provider");
        }
        Provider p = Security.getProvider(provider);
        if (p == null) {
            throw new NoSuchProviderException("No such provider: " +
                                              provider);
        }
        return getInstance(transformation, p);
    }

    
Returns a Cipher object that implements the specified
transformation.
 A new Cipher object encapsulating the
CipherSpi implementation from the specified Provider
object is returned.  Note that the specified Provider object
does not have to be registered in the provider list.
Params:
transformation – the name of the transformation,
e.g., AES/CBC/PKCS5Padding.
See Appendix A in the

Java Cryptography Architecture Reference Guide
for information about standard transformation names.
provider – the provider.
Throws:
NoSuchAlgorithmException – if transformation
         is null, empty, in an invalid format,
         or if a CipherSpi implementation for the specified algorithm
         is not available from the specified Provider object.
NoSuchPaddingException – if transformation
         contains a padding scheme that is not available.
IllegalArgumentException – if the provider
         is null.
See Also:
Provider
Returns:
a cipher that implements the requested transformation./**
     * Returns a <code>Cipher</code> object that implements the specified
     * transformation.
     *
     * <p> A new Cipher object encapsulating the
     * CipherSpi implementation from the specified Provider
     * object is returned.  Note that the specified Provider object
     * does not have to be registered in the provider list.
     *
     * @param transformation the name of the transformation,
     * e.g., <i>AES/CBC/PKCS5Padding</i>.
     * See Appendix A in the
     * <a href=
     *   "{@docRoot}/../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture Reference Guide</a>
     * for information about standard transformation names.
     *
     * @param provider the provider.
     *
     * @return a cipher that implements the requested transformation.
     *
     * @exception NoSuchAlgorithmException if <code>transformation</code>
     *          is null, empty, in an invalid format,
     *          or if a CipherSpi implementation for the specified algorithm
     *          is not available from the specified Provider object.
     *
     * @exception NoSuchPaddingException if <code>transformation</code>
     *          contains a padding scheme that is not available.
     *
     * @exception IllegalArgumentException if the <code>provider</code>
     *          is null.
     *
     * @see java.security.Provider
     */
    public static final Cipher getInstance(String transformation,
                                           Provider provider)
            throws NoSuchAlgorithmException, NoSuchPaddingException
    {
        if (provider == null) {
            throw new IllegalArgumentException("Missing provider");
        }
        Exception failure = null;
        List<Transform> transforms = getTransforms(transformation);
        boolean providerChecked = false;
        String paddingError = null;
        for (Transform tr : transforms) {
            Service s = provider.getService("Cipher", tr.transform);
            if (s == null) {
                continue;
            }
            if (providerChecked == false) {
                // for compatibility, first do the lookup and then verify
                // the provider. this makes the difference between a NSAE
                // and a SecurityException if the
                // provider does not support the algorithm.
                Exception ve = JceSecurity.getVerificationResult(provider);
                if (ve != null) {
                    String msg = "JCE cannot authenticate the provider "
                        + provider.getName();
                    throw new SecurityException(msg, ve);
                }
                providerChecked = true;
            }
            if (tr.supportsMode(s) == S_NO) {
                continue;
            }
            if (tr.supportsPadding(s) == S_NO) {
                paddingError = tr.pad;
                continue;
            }
            try {
                CipherSpi spi = (CipherSpi)s.newInstance(null);
                tr.setModePadding(spi);
                Cipher cipher = new Cipher(spi, transformation);
                cipher.provider = s.getProvider();
                cipher.initCryptoPermission();
                return cipher;
            } catch (Exception e) {
                failure = e;
            }
        }

        // throw NoSuchPaddingException if the problem is with padding
        if (failure instanceof NoSuchPaddingException) {
            throw (NoSuchPaddingException)failure;
        }
        if (paddingError != null) {
            throw new NoSuchPaddingException
                ("Padding not supported: " + paddingError);
        }
        throw new NoSuchAlgorithmException
                ("No such algorithm: " + transformation, failure);
    }

    // If the requested crypto service is export-controlled,
    // determine the maximum allowable keysize.
    private void initCryptoPermission() throws NoSuchAlgorithmException {
        if (JceSecurity.isRestricted() == false) {
            cryptoPerm = CryptoAllPermission.INSTANCE;
            exmech = null;
            return;
        }
        cryptoPerm = getConfiguredPermission(transformation);
        // Instantiate the exemption mechanism (if required)
        String exmechName = cryptoPerm.getExemptionMechanism();
        if (exmechName != null) {
            exmech = ExemptionMechanism.getInstance(exmechName);
        }
    }

    // max number of debug warnings to print from chooseFirstProvider()
    private static int warnCount = 10;

    
Choose the Spi from the first provider available. Used if
delayed provider selection is not possible because init()
is not the first method called.
/**
     * Choose the Spi from the first provider available. Used if
     * delayed provider selection is not possible because init()
     * is not the first method called.
     */
    void chooseFirstProvider() {
        if (spi != null) {
            return;
        }
        synchronized (lock) {
            if (spi != null) {
                return;
            }
            if (debug != null) {
                int w = --warnCount;
                if (w >= 0) {
                    debug.println("Cipher.init() not first method "
                        + "called, disabling delayed provider selection");
                    if (w == 0) {
                        debug.println("Further warnings of this type will "
                            + "be suppressed");
                    }
                    new Exception("Call trace").printStackTrace();
                }
            }
            Exception lastException = null;
            while ((firstService != null) || serviceIterator.hasNext()) {
                Service s;
                CipherSpi thisSpi;
                if (firstService != null) {
                    s = firstService;
                    thisSpi = firstSpi;
                    firstService = null;
                    firstSpi = null;
                } else {
                    s = serviceIterator.next();
                    thisSpi = null;
                }
                if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                    continue;
                }
                Transform tr = getTransform(s, transforms);
                if (tr == null) {
                    // should never happen
                    continue;
                }
                if (tr.supportsModePadding(s) == S_NO) {
                    continue;
                }
                try {
                    if (thisSpi == null) {
                        Object obj = s.newInstance(null);
                        if (obj instanceof CipherSpi == false) {
                            continue;
                        }
                        thisSpi = (CipherSpi)obj;
                    }
                    tr.setModePadding(thisSpi);
                    initCryptoPermission();
                    spi = thisSpi;
                    provider = s.getProvider();
                    // not needed any more
                    firstService = null;
                    serviceIterator = null;
                    transforms = null;
                    return;
                } catch (Exception e) {
                    lastException = e;
                }
            }
            ProviderException e = new ProviderException
                    ("Could not construct CipherSpi instance");
            if (lastException != null) {
                e.initCause(lastException);
            }
            throw e;
        }
    }

    private final static int I_KEY       = 1;
    private final static int I_PARAMSPEC = 2;
    private final static int I_PARAMS    = 3;
    private final static int I_CERT      = 4;

    private void implInit(CipherSpi thisSpi, int type, int opmode, Key key,
            AlgorithmParameterSpec paramSpec, AlgorithmParameters params,
            SecureRandom random) throws InvalidKeyException,
            InvalidAlgorithmParameterException {
        switch (type) {
        case I_KEY:
            checkCryptoPerm(thisSpi, key);
            thisSpi.engineInit(opmode, key, random);
            break;
        case I_PARAMSPEC:
            checkCryptoPerm(thisSpi, key, paramSpec);
            thisSpi.engineInit(opmode, key, paramSpec, random);
            break;
        case I_PARAMS:
            checkCryptoPerm(thisSpi, key, params);
            thisSpi.engineInit(opmode, key, params, random);
            break;
        case I_CERT:
            checkCryptoPerm(thisSpi, key);
            thisSpi.engineInit(opmode, key, random);
            break;
        default:
            throw new AssertionError("Internal Cipher error: " + type);
        }
    }

    private void chooseProvider(int initType, int opmode, Key key,
            AlgorithmParameterSpec paramSpec,
            AlgorithmParameters params, SecureRandom random)
            throws InvalidKeyException, InvalidAlgorithmParameterException {
        synchronized (lock) {
            if (spi != null) {
                implInit(spi, initType, opmode, key, paramSpec, params, random);
                return;
            }
            Exception lastException = null;
            while ((firstService != null) || serviceIterator.hasNext()) {
                Service s;
                CipherSpi thisSpi;
                if (firstService != null) {
                    s = firstService;
                    thisSpi = firstSpi;
                    firstService = null;
                    firstSpi = null;
                } else {
                    s = serviceIterator.next();
                    thisSpi = null;
                }
                // if provider says it does not support this key, ignore it
                if (s.supportsParameter(key) == false) {
                    continue;
                }
                if (JceSecurity.canUseProvider(s.getProvider()) == false) {
                    continue;
                }
                Transform tr = getTransform(s, transforms);
                if (tr == null) {
                    // should never happen
                    continue;
                }
                if (tr.supportsModePadding(s) == S_NO) {
                    continue;
                }
                try {
                    if (thisSpi == null) {
                        thisSpi = (CipherSpi)s.newInstance(null);
                    }
                    tr.setModePadding(thisSpi);
                    initCryptoPermission();
                    implInit(thisSpi, initType, opmode, key, paramSpec,
                                                        params, random);
                    provider = s.getProvider();
                    this.spi = thisSpi;
                    firstService = null;
                    serviceIterator = null;
                    transforms = null;
                    return;
                } catch (Exception e) {
                    // NoSuchAlgorithmException from newInstance()
                    // InvalidKeyException from init()
                    // RuntimeException (ProviderException) from init()
                    // SecurityException from crypto permission check
                    if (lastException == null) {
                        lastException = e;
                    }
                }
            }
            // no working provider found, fail
            if (lastException instanceof InvalidKeyException) {
                throw (InvalidKeyException)lastException;
            }
            if (lastException instanceof InvalidAlgorithmParameterException) {
                throw (InvalidAlgorithmParameterException)lastException;
            }
            if (lastException instanceof RuntimeException) {
                throw (RuntimeException)lastException;
            }
            String kName = (key != null) ? key.getClass().getName() : "(null)";
            throw new InvalidKeyException
                ("No installed provider supports this key: "
                + kName, lastException);
        }
    }

    
Returns the provider of this Cipher object.
Returns:
the provider of this Cipher object/**
     * Returns the provider of this <code>Cipher</code> object.
     *
     * @return the provider of this <code>Cipher</code> object
     */
    public final Provider getProvider() {
        chooseFirstProvider();
        return this.provider;
    }

    
Returns the algorithm name of this Cipher object.
This is the same name that was specified in one of the
getInstance calls that created this Cipher
object..
Returns:
the algorithm name of this Cipher object./**
     * Returns the algorithm name of this <code>Cipher</code> object.
     *
     * <p>This is the same name that was specified in one of the
     * <code>getInstance</code> calls that created this <code>Cipher</code>
     * object..
     *
     * @return the algorithm name of this <code>Cipher</code> object.
     */
    public final String getAlgorithm() {
        return this.transformation;
    }

    
Returns the block size (in bytes).
Returns:
the block size (in bytes), or 0 if the underlying algorithm is
not a block cipher/**
     * Returns the block size (in bytes).
     *
     * @return the block size (in bytes), or 0 if the underlying algorithm is
     * not a block cipher
     */
    public final int getBlockSize() {
        chooseFirstProvider();
        return spi.engineGetBlockSize();
    }

    
Returns the length in bytes that an output buffer would need to be in
order to hold the result of the next update or
doFinal operation, given the input length
inputLen (in bytes).
This call takes into account any unprocessed (buffered) data from a
previous update call, and padding.
The actual output length of the next update or
doFinal call may be smaller than the length returned by
this method.
Params:
inputLen – the input length (in bytes)
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not yet been initialized)
Returns:
the required output buffer size (in bytes)/**
     * Returns the length in bytes that an output buffer would need to be in
     * order to hold the result of the next <code>update</code> or
     * <code>doFinal</code> operation, given the input length
     * <code>inputLen</code> (in bytes).
     *
     * <p>This call takes into account any unprocessed (buffered) data from a
     * previous <code>update</code> call, and padding.
     *
     * <p>The actual output length of the next <code>update</code> or
     * <code>doFinal</code> call may be smaller than the length returned by
     * this method.
     *
     * @param inputLen the input length (in bytes)
     *
     * @return the required output buffer size (in bytes)
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not yet been initialized)
     */
    public final int getOutputSize(int inputLen) {

        if (!initialized && !(this instanceof NullCipher)) {
            throw new IllegalStateException("Cipher not initialized");
        }
        if (inputLen < 0) {
            throw new IllegalArgumentException("Input size must be equal " +
                                               "to or greater than zero");
        }
        chooseFirstProvider();
        return spi.engineGetOutputSize(inputLen);
    }

    
Returns the initialization vector (IV) in a new buffer.
This is useful in the case where a random IV was created,
or in the context of password-based encryption or
decryption, where the IV is derived from a user-supplied password.
Returns:
the initialization vector in a new buffer, or null if the
underlying algorithm does not use an IV, or if the IV has not yet
been set./**
     * Returns the initialization vector (IV) in a new buffer.
     *
     * <p>This is useful in the case where a random IV was created,
     * or in the context of password-based encryption or
     * decryption, where the IV is derived from a user-supplied password.
     *
     * @return the initialization vector in a new buffer, or null if the
     * underlying algorithm does not use an IV, or if the IV has not yet
     * been set.
     */
    public final byte[] getIV() {
        chooseFirstProvider();
        return spi.engineGetIV();
    }

    
Returns the parameters used with this cipher.
The returned parameters may be the same that were used to initialize
this cipher, or may contain a combination of default and random
parameter values used by the underlying cipher implementation if this
cipher requires algorithm parameters but was not initialized with any.
Returns:
the parameters used with this cipher, or null if this cipher
does not use any parameters./**
     * Returns the parameters used with this cipher.
     *
     * <p>The returned parameters may be the same that were used to initialize
     * this cipher, or may contain a combination of default and random
     * parameter values used by the underlying cipher implementation if this
     * cipher requires algorithm parameters but was not initialized with any.
     *
     * @return the parameters used with this cipher, or null if this cipher
     * does not use any parameters.
     */
    public final AlgorithmParameters getParameters() {
        chooseFirstProvider();
        return spi.engineGetParameters();
    }

    
Returns the exemption mechanism object used with this cipher.
Returns:
the exemption mechanism object used with this cipher, or
null if this cipher does not use any exemption mechanism./**
     * Returns the exemption mechanism object used with this cipher.
     *
     * @return the exemption mechanism object used with this cipher, or
     * null if this cipher does not use any exemption mechanism.
     */
    public final ExemptionMechanism getExemptionMechanism() {
        chooseFirstProvider();
        return exmech;
    }

    //
    // Crypto permission check code below
    //
    private void checkCryptoPerm(CipherSpi checkSpi, Key key)
            throws InvalidKeyException {
        if (cryptoPerm == CryptoAllPermission.INSTANCE) {
            return;
        }
        // Check if key size and default parameters are within legal limits
        AlgorithmParameterSpec params;
        try {
            params = getAlgorithmParameterSpec(checkSpi.engineGetParameters());
        } catch (InvalidParameterSpecException ipse) {
            throw new InvalidKeyException
                ("Unsupported default algorithm parameters");
        }
        if (!passCryptoPermCheck(checkSpi, key, params)) {
            throw new InvalidKeyException(
                "Illegal key size or default parameters");
        }
    }

    private void checkCryptoPerm(CipherSpi checkSpi, Key key,
            AlgorithmParameterSpec params) throws InvalidKeyException,
            InvalidAlgorithmParameterException {
        if (cryptoPerm == CryptoAllPermission.INSTANCE) {
            return;
        }
        // Determine keysize and check if it is within legal limits
        if (!passCryptoPermCheck(checkSpi, key, null)) {
            throw new InvalidKeyException("Illegal key size");
        }
        if ((params != null) && (!passCryptoPermCheck(checkSpi, key, params))) {
            throw new InvalidAlgorithmParameterException("Illegal parameters");
        }
    }

    private void checkCryptoPerm(CipherSpi checkSpi, Key key,
            AlgorithmParameters params)
            throws InvalidKeyException, InvalidAlgorithmParameterException {
        if (cryptoPerm == CryptoAllPermission.INSTANCE) {
            return;
        }
        // Convert the specified parameters into specs and then delegate.
        AlgorithmParameterSpec pSpec;
        try {
            pSpec = getAlgorithmParameterSpec(params);
        } catch (InvalidParameterSpecException ipse) {
            throw new InvalidAlgorithmParameterException
                ("Failed to retrieve algorithm parameter specification");
        }
        checkCryptoPerm(checkSpi, key, pSpec);
    }

    private boolean passCryptoPermCheck(CipherSpi checkSpi, Key key,
                                        AlgorithmParameterSpec params)
            throws InvalidKeyException {
        String em = cryptoPerm.getExemptionMechanism();
        int keySize = checkSpi.engineGetKeySize(key);
        // Use the "algorithm" component of the cipher
        // transformation so that the perm check would
        // work when the key has the "aliased" algo.
        String algComponent;
        int index = transformation.indexOf('/');
        if (index != -1) {
            algComponent = transformation.substring(0, index);
        } else {
            algComponent = transformation;
        }
        CryptoPermission checkPerm =
            new CryptoPermission(algComponent, keySize, params, em);

        if (!cryptoPerm.implies(checkPerm)) {
            if (debug != null) {
                debug.println("Crypto Permission check failed");
                debug.println("granted: " + cryptoPerm);
                debug.println("requesting: " + checkPerm);
            }
            return false;
        }
        if (exmech == null) {
            return true;
        }
        try {
            if (!exmech.isCryptoAllowed(key)) {
                if (debug != null) {
                    debug.println(exmech.getName() + " isn't enforced");
                }
                return false;
            }
        } catch (ExemptionMechanismException eme) {
            if (debug != null) {
                debug.println("Cannot determine whether "+
                              exmech.getName() + " has been enforced");
                eme.printStackTrace();
            }
            return false;
        }
        return true;
    }

    // check if opmode is one of the defined constants
    // throw InvalidParameterExeption if not
    private static void checkOpmode(int opmode) {
        if ((opmode < ENCRYPT_MODE) || (opmode > UNWRAP_MODE)) {
            throw new InvalidParameterException("Invalid operation mode");
        }
    }

    
Initializes this cipher with a key.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending
on the value of opmode.
If this cipher requires any algorithm parameters that cannot be
derived from the given key, the underlying cipher
implementation is supposed to generate the required parameters itself
(using provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidKeyException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.) 
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of
the following:
ENCRYPT_MODE, DECRYPT_MODE,
WRAP_MODE or UNWRAP_MODE)
key – the key
Throws:
InvalidKeyException – if the given key is inappropriate for
initializing this cipher, or if this cipher is being initialized for
decryption and requires algorithm parameters that cannot be
determined from the given key, or if the given key has a keysize that
exceeds the maximum allowable keysize (as determined from the
configured jurisdiction policy files)./**
     * Initializes this cipher with a key.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If this cipher requires any algorithm parameters that cannot be
     * derived from the given <code>key</code>, the underlying cipher
     * implementation is supposed to generate the required parameters itself
     * (using provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidKeyException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them using the {@link SecureRandom <code>SecureRandom</code>}
     * implementation of the highest-priority
     * installed provider as the source of randomness.
     * (If none of the installed providers supply an implementation of
     * SecureRandom, a system-provided source of randomness will be used.)
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of
     * the following:
     * <code>ENCRYPT_MODE</code>, <code>DECRYPT_MODE</code>,
     * <code>WRAP_MODE</code> or <code>UNWRAP_MODE</code>)
     * @param key the key
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher, or if this cipher is being initialized for
     * decryption and requires algorithm parameters that cannot be
     * determined from the given key, or if the given key has a keysize that
     * exceeds the maximum allowable keysize (as determined from the
     * configured jurisdiction policy files).
     */
    public final void init(int opmode, Key key) throws InvalidKeyException {
        init(opmode, key, JceSecurity.RANDOM);
    }

    
Initializes this cipher with a key and a source of randomness.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or  key unwrapping, depending
on the value of opmode.
If this cipher requires any algorithm parameters that cannot be
derived from the given key, the underlying cipher
implementation is supposed to generate the required parameters itself
(using provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidKeyException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random.
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following:
ENCRYPT_MODE, DECRYPT_MODE,
WRAP_MODE or UNWRAP_MODE)
key – the encryption key
random – the source of randomness
Throws:
InvalidKeyException – if the given key is inappropriate for
initializing this cipher, or if this cipher is being initialized for
decryption and requires algorithm parameters that cannot be
determined from the given key, or if the given key has a keysize that
exceeds the maximum allowable keysize (as determined from the
configured jurisdiction policy files)./**
     * Initializes this cipher with a key and a source of randomness.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or  key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If this cipher requires any algorithm parameters that cannot be
     * derived from the given <code>key</code>, the underlying cipher
     * implementation is supposed to generate the required parameters itself
     * (using provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidKeyException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them from <code>random</code>.
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following:
     * <code>ENCRYPT_MODE</code>, <code>DECRYPT_MODE</code>,
     * <code>WRAP_MODE</code> or <code>UNWRAP_MODE</code>)
     * @param key the encryption key
     * @param random the source of randomness
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher, or if this cipher is being initialized for
     * decryption and requires algorithm parameters that cannot be
     * determined from the given key, or if the given key has a keysize that
     * exceeds the maximum allowable keysize (as determined from the
     * configured jurisdiction policy files).
     */
    public final void init(int opmode, Key key, SecureRandom random)
            throws InvalidKeyException
    {
        initialized = false;
        checkOpmode(opmode);

        if (spi != null) {
            checkCryptoPerm(spi, key);
            spi.engineInit(opmode, key, random);
        } else {
            try {
                chooseProvider(I_KEY, opmode, key, null, null, random);
            } catch (InvalidAlgorithmParameterException e) {
                // should never occur
                throw new InvalidKeyException(e);
            }
        }

        initialized = true;
        this.opmode = opmode;
    }

    
Initializes this cipher with a key and a set of algorithm
parameters.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or  key unwrapping, depending
on the value of opmode.
If this cipher requires any algorithm parameters and
params is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidAlgorithmParameterException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.) 
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following:
ENCRYPT_MODE, DECRYPT_MODE,
WRAP_MODE or UNWRAP_MODE)
key – the encryption key
params – the algorithm parameters
Throws:
InvalidKeyException – if the given key is inappropriate for
initializing this cipher, or its keysize exceeds the maximum allowable
keysize (as determined from the configured jurisdiction policy files).
InvalidAlgorithmParameterException – if the given algorithm
parameters are inappropriate for this cipher,
or this cipher is being initialized for decryption and requires
algorithm parameters and params is null, or the given
algorithm parameters imply a cryptographic strength that would exceed
the legal limits (as determined from the configured jurisdiction
policy files)./**
     * Initializes this cipher with a key and a set of algorithm
     * parameters.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or  key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If this cipher requires any algorithm parameters and
     * <code>params</code> is null, the underlying cipher implementation is
     * supposed to generate the required parameters itself (using
     * provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidAlgorithmParameterException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them using the {@link SecureRandom <code>SecureRandom</code>}
     * implementation of the highest-priority
     * installed provider as the source of randomness.
     * (If none of the installed providers supply an implementation of
     * SecureRandom, a system-provided source of randomness will be used.)
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following:
     * <code>ENCRYPT_MODE</code>, <code>DECRYPT_MODE</code>,
     * <code>WRAP_MODE</code> or <code>UNWRAP_MODE</code>)
     * @param key the encryption key
     * @param params the algorithm parameters
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher, or its keysize exceeds the maximum allowable
     * keysize (as determined from the configured jurisdiction policy files).
     * @exception InvalidAlgorithmParameterException if the given algorithm
     * parameters are inappropriate for this cipher,
     * or this cipher is being initialized for decryption and requires
     * algorithm parameters and <code>params</code> is null, or the given
     * algorithm parameters imply a cryptographic strength that would exceed
     * the legal limits (as determined from the configured jurisdiction
     * policy files).
     */
    public final void init(int opmode, Key key, AlgorithmParameterSpec params)
            throws InvalidKeyException, InvalidAlgorithmParameterException
    {
        init(opmode, key, params, JceSecurity.RANDOM);
    }

    
Initializes this cipher with a key, a set of algorithm
parameters, and a source of randomness.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or  key unwrapping, depending
on the value of opmode.
If this cipher requires any algorithm parameters and
params is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidAlgorithmParameterException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random.
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following:
ENCRYPT_MODE, DECRYPT_MODE,
WRAP_MODE or UNWRAP_MODE)
key – the encryption key
params – the algorithm parameters
random – the source of randomness
Throws:
InvalidKeyException – if the given key is inappropriate for
initializing this cipher, or its keysize exceeds the maximum allowable
keysize (as determined from the configured jurisdiction policy files).
InvalidAlgorithmParameterException – if the given algorithm
parameters are inappropriate for this cipher,
or this cipher is being initialized for decryption and requires
algorithm parameters and params is null, or the given
algorithm parameters imply a cryptographic strength that would exceed
the legal limits (as determined from the configured jurisdiction
policy files)./**
     * Initializes this cipher with a key, a set of algorithm
     * parameters, and a source of randomness.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or  key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If this cipher requires any algorithm parameters and
     * <code>params</code> is null, the underlying cipher implementation is
     * supposed to generate the required parameters itself (using
     * provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidAlgorithmParameterException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them from <code>random</code>.
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following:
     * <code>ENCRYPT_MODE</code>, <code>DECRYPT_MODE</code>,
     * <code>WRAP_MODE</code> or <code>UNWRAP_MODE</code>)
     * @param key the encryption key
     * @param params the algorithm parameters
     * @param random the source of randomness
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher, or its keysize exceeds the maximum allowable
     * keysize (as determined from the configured jurisdiction policy files).
     * @exception InvalidAlgorithmParameterException if the given algorithm
     * parameters are inappropriate for this cipher,
     * or this cipher is being initialized for decryption and requires
     * algorithm parameters and <code>params</code> is null, or the given
     * algorithm parameters imply a cryptographic strength that would exceed
     * the legal limits (as determined from the configured jurisdiction
     * policy files).
     */
    public final void init(int opmode, Key key, AlgorithmParameterSpec params,
                           SecureRandom random)
            throws InvalidKeyException, InvalidAlgorithmParameterException
    {
        initialized = false;
        checkOpmode(opmode);

        if (spi != null) {
            checkCryptoPerm(spi, key, params);
            spi.engineInit(opmode, key, params, random);
        } else {
            chooseProvider(I_PARAMSPEC, opmode, key, params, null, random);
        }

        initialized = true;
        this.opmode = opmode;
    }

    
Initializes this cipher with a key and a set of algorithm
parameters.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or  key unwrapping, depending
on the value of opmode.
If this cipher requires any algorithm parameters and
params is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidAlgorithmParameterException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.) 
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following: ENCRYPT_MODE,
DECRYPT_MODE, WRAP_MODE
or UNWRAP_MODE)
key – the encryption key
params – the algorithm parameters
Throws:
InvalidKeyException – if the given key is inappropriate for
initializing this cipher, or its keysize exceeds the maximum allowable
keysize (as determined from the configured jurisdiction policy files).
InvalidAlgorithmParameterException – if the given algorithm
parameters are inappropriate for this cipher,
or this cipher is being initialized for decryption and requires
algorithm parameters and params is null, or the given
algorithm parameters imply a cryptographic strength that would exceed
the legal limits (as determined from the configured jurisdiction
policy files)./**
     * Initializes this cipher with a key and a set of algorithm
     * parameters.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or  key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If this cipher requires any algorithm parameters and
     * <code>params</code> is null, the underlying cipher implementation is
     * supposed to generate the required parameters itself (using
     * provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidAlgorithmParameterException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them using the {@link SecureRandom <code>SecureRandom</code>}
     * implementation of the highest-priority
     * installed provider as the source of randomness.
     * (If none of the installed providers supply an implementation of
     * SecureRandom, a system-provided source of randomness will be used.)
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following: <code>ENCRYPT_MODE</code>,
     * <code>DECRYPT_MODE</code>, <code>WRAP_MODE</code>
     * or <code>UNWRAP_MODE</code>)
     * @param key the encryption key
     * @param params the algorithm parameters
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher, or its keysize exceeds the maximum allowable
     * keysize (as determined from the configured jurisdiction policy files).
     * @exception InvalidAlgorithmParameterException if the given algorithm
     * parameters are inappropriate for this cipher,
     * or this cipher is being initialized for decryption and requires
     * algorithm parameters and <code>params</code> is null, or the given
     * algorithm parameters imply a cryptographic strength that would exceed
     * the legal limits (as determined from the configured jurisdiction
     * policy files).
     */
    public final void init(int opmode, Key key, AlgorithmParameters params)
            throws InvalidKeyException, InvalidAlgorithmParameterException
    {
        init(opmode, key, params, JceSecurity.RANDOM);
    }

    
Initializes this cipher with a key, a set of algorithm
parameters, and a source of randomness.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or  key unwrapping, depending
on the value of opmode.
If this cipher requires any algorithm parameters and
params is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidAlgorithmParameterException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random.
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following: ENCRYPT_MODE,
DECRYPT_MODE, WRAP_MODE
or UNWRAP_MODE)
key – the encryption key
params – the algorithm parameters
random – the source of randomness
Throws:
InvalidKeyException – if the given key is inappropriate for
initializing this cipher, or its keysize exceeds the maximum allowable
keysize (as determined from the configured jurisdiction policy files).
InvalidAlgorithmParameterException – if the given algorithm
parameters are inappropriate for this cipher,
or this cipher is being initialized for decryption and requires
algorithm parameters and params is null, or the given
algorithm parameters imply a cryptographic strength that would exceed
the legal limits (as determined from the configured jurisdiction
policy files)./**
     * Initializes this cipher with a key, a set of algorithm
     * parameters, and a source of randomness.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or  key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If this cipher requires any algorithm parameters and
     * <code>params</code> is null, the underlying cipher implementation is
     * supposed to generate the required parameters itself (using
     * provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidAlgorithmParameterException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them from <code>random</code>.
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following: <code>ENCRYPT_MODE</code>,
     * <code>DECRYPT_MODE</code>, <code>WRAP_MODE</code>
     * or <code>UNWRAP_MODE</code>)
     * @param key the encryption key
     * @param params the algorithm parameters
     * @param random the source of randomness
     *
     * @exception InvalidKeyException if the given key is inappropriate for
     * initializing this cipher, or its keysize exceeds the maximum allowable
     * keysize (as determined from the configured jurisdiction policy files).
     * @exception InvalidAlgorithmParameterException if the given algorithm
     * parameters are inappropriate for this cipher,
     * or this cipher is being initialized for decryption and requires
     * algorithm parameters and <code>params</code> is null, or the given
     * algorithm parameters imply a cryptographic strength that would exceed
     * the legal limits (as determined from the configured jurisdiction
     * policy files).
     */
    public final void init(int opmode, Key key, AlgorithmParameters params,
                           SecureRandom random)
            throws InvalidKeyException, InvalidAlgorithmParameterException
    {
        initialized = false;
        checkOpmode(opmode);

        if (spi != null) {
            checkCryptoPerm(spi, key, params);
            spi.engineInit(opmode, key, params, random);
        } else {
            chooseProvider(I_PARAMS, opmode, key, null, params, random);
        }

        initialized = true;
        this.opmode = opmode;
    }

    
Initializes this cipher with the public key from the given certificate.
 The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or  key unwrapping, depending
on the value of opmode.
If the certificate is of type X.509 and has a key usage
extension field marked as critical, and the value of the key usage
extension field implies that the public key in
the certificate and its corresponding private key are not
supposed to be used for the operation represented by the value
of opmode,
an InvalidKeyException
is thrown.
 If this cipher requires any algorithm parameters that cannot be
derived from the public key in the given certificate, the underlying
cipher
implementation is supposed to generate the required parameters itself
(using provider-specific default or ramdom values) if it is being
initialized for encryption or key wrapping, and raise an 
InvalidKeyException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them using the
SecureRandom
implementation of the highest-priority
installed provider as the source of randomness.
(If none of the installed providers supply an implementation of
SecureRandom, a system-provided source of randomness will be used.)
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following:
ENCRYPT_MODE, DECRYPT_MODE,
WRAP_MODE or UNWRAP_MODE)
certificate – the certificate
Throws:
InvalidKeyException – if the public key in the given
certificate is inappropriate for initializing this cipher, or this
cipher is being initialized for decryption or unwrapping keys and
requires algorithm parameters that cannot be determined from the
public key in the given certificate, or the keysize of the public key
in the given certificate has a keysize that exceeds the maximum
allowable keysize (as determined by the configured jurisdiction policy
files)./**
     * Initializes this cipher with the public key from the given certificate.
     * <p> The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping or  key unwrapping, depending
     * on the value of <code>opmode</code>.
     *
     * <p>If the certificate is of type X.509 and has a <i>key usage</i>
     * extension field marked as critical, and the value of the <i>key usage</i>
     * extension field implies that the public key in
     * the certificate and its corresponding private key are not
     * supposed to be used for the operation represented by the value
     * of <code>opmode</code>,
     * an <code>InvalidKeyException</code>
     * is thrown.
     *
     * <p> If this cipher requires any algorithm parameters that cannot be
     * derived from the public key in the given certificate, the underlying
     * cipher
     * implementation is supposed to generate the required parameters itself
     * (using provider-specific default or ramdom values) if it is being
     * initialized for encryption or key wrapping, and raise an <code>
     * InvalidKeyException</code> if it is being initialized for decryption or
     * key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them using the
     * <code>SecureRandom</code>
     * implementation of the highest-priority
     * installed provider as the source of randomness.
     * (If none of the installed providers supply an implementation of
     * SecureRandom, a system-provided source of randomness will be used.)
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following:
     * <code>ENCRYPT_MODE</code>, <code>DECRYPT_MODE</code>,
     * <code>WRAP_MODE</code> or <code>UNWRAP_MODE</code>)
     * @param certificate the certificate
     *
     * @exception InvalidKeyException if the public key in the given
     * certificate is inappropriate for initializing this cipher, or this
     * cipher is being initialized for decryption or unwrapping keys and
     * requires algorithm parameters that cannot be determined from the
     * public key in the given certificate, or the keysize of the public key
     * in the given certificate has a keysize that exceeds the maximum
     * allowable keysize (as determined by the configured jurisdiction policy
     * files).
     */
    public final void init(int opmode, Certificate certificate)
            throws InvalidKeyException
    {
        init(opmode, certificate, JceSecurity.RANDOM);
    }

    
Initializes this cipher with the public key from the given certificate
and
a source of randomness.
The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping
or key unwrapping, depending on
the value of opmode.
If the certificate is of type X.509 and has a key usage
extension field marked as critical, and the value of the key usage
extension field implies that the public key in
the certificate and its corresponding private key are not
supposed to be used for the operation represented by the value of
opmode,
an InvalidKeyException
is thrown.
If this cipher requires any algorithm parameters that cannot be
derived from the public key in the given certificate,
the underlying cipher
implementation is supposed to generate the required parameters itself
(using provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
InvalidKeyException if it is being initialized for decryption or key unwrapping. The generated parameters can be retrieved using getParameters or getIV (if the parameter is an IV). 
If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from random.
Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.
Params:
opmode – the operation mode of this cipher (this is one of the
following:
ENCRYPT_MODE, DECRYPT_MODE,
WRAP_MODE or UNWRAP_MODE)
certificate – the certificate
random – the source of randomness
Throws:
InvalidKeyException – if the public key in the given
certificate is inappropriate for initializing this cipher, or this
cipher is being initialized for decryption or unwrapping keys and
requires algorithm parameters that cannot be determined from the
public key in the given certificate, or the keysize of the public key
in the given certificate has a keysize that exceeds the maximum
allowable keysize (as determined by the configured jurisdiction policy
files)./**
     * Initializes this cipher with the public key from the given certificate
     * and
     * a source of randomness.
     *
     * <p>The cipher is initialized for one of the following four operations:
     * encryption, decryption, key wrapping
     * or key unwrapping, depending on
     * the value of <code>opmode</code>.
     *
     * <p>If the certificate is of type X.509 and has a <i>key usage</i>
     * extension field marked as critical, and the value of the <i>key usage</i>
     * extension field implies that the public key in
     * the certificate and its corresponding private key are not
     * supposed to be used for the operation represented by the value of
     * <code>opmode</code>,
     * an <code>InvalidKeyException</code>
     * is thrown.
     *
     * <p>If this cipher requires any algorithm parameters that cannot be
     * derived from the public key in the given <code>certificate</code>,
     * the underlying cipher
     * implementation is supposed to generate the required parameters itself
     * (using provider-specific default or random values) if it is being
     * initialized for encryption or key wrapping, and raise an
     * <code>InvalidKeyException</code> if it is being
     * initialized for decryption or key unwrapping.
     * The generated parameters can be retrieved using
     * {@link #getParameters() getParameters} or
     * {@link #getIV() getIV} (if the parameter is an IV).
     *
     * <p>If this cipher (including its underlying feedback or padding scheme)
     * requires any random bytes (e.g., for parameter generation), it will get
     * them from <code>random</code>.
     *
     * <p>Note that when a Cipher object is initialized, it loses all
     * previously-acquired state. In other words, initializing a Cipher is
     * equivalent to creating a new instance of that Cipher and initializing
     * it.
     *
     * @param opmode the operation mode of this cipher (this is one of the
     * following:
     * <code>ENCRYPT_MODE</code>, <code>DECRYPT_MODE</code>,
     * <code>WRAP_MODE</code> or <code>UNWRAP_MODE</code>)
     * @param certificate the certificate
     * @param random the source of randomness
     *
     * @exception InvalidKeyException if the public key in the given
     * certificate is inappropriate for initializing this cipher, or this
     * cipher is being initialized for decryption or unwrapping keys and
     * requires algorithm parameters that cannot be determined from the
     * public key in the given certificate, or the keysize of the public key
     * in the given certificate has a keysize that exceeds the maximum
     * allowable keysize (as determined by the configured jurisdiction policy
     * files).
     */
    public final void init(int opmode, Certificate certificate,
                           SecureRandom random)
            throws InvalidKeyException
    {
        initialized = false;
        checkOpmode(opmode);

        // Check key usage if the certificate is of
        // type X.509.
        if (certificate instanceof java.security.cert.X509Certificate) {
            // Check whether the cert has a key usage extension
            // marked as a critical extension.
            X509Certificate cert = (X509Certificate)certificate;
            Set<String> critSet = cert.getCriticalExtensionOIDs();

            if (critSet != null && !critSet.isEmpty()
                && critSet.contains(KEY_USAGE_EXTENSION_OID)) {
                boolean[] keyUsageInfo = cert.getKeyUsage();
                // keyUsageInfo[2] is for keyEncipherment;
                // keyUsageInfo[3] is for dataEncipherment.
                if ((keyUsageInfo != null) &&
                    (((opmode == Cipher.ENCRYPT_MODE) &&
                      (keyUsageInfo.length > 3) &&
                      (keyUsageInfo[3] == false)) ||
                     ((opmode == Cipher.WRAP_MODE) &&
                      (keyUsageInfo.length > 2) &&
                      (keyUsageInfo[2] == false)))) {
                    throw new InvalidKeyException("Wrong key usage");
                }
            }
        }

        PublicKey publicKey =
            (certificate==null? null:certificate.getPublicKey());

        if (spi != null) {
            checkCryptoPerm(spi, publicKey);
            spi.engineInit(opmode, publicKey, random);
        } else {
            try {
                chooseProvider(I_CERT, opmode, publicKey, null, null, random);
            } catch (InvalidAlgorithmParameterException e) {
                // should never occur
                throw new InvalidKeyException(e);
            }
        }

        initialized = true;
        this.opmode = opmode;
    }

    
Ensures that Cipher is in a valid state for update() and doFinal()
calls - should be initialized and in ENCRYPT_MODE or DECRYPT_MODE.
Throws:
IllegalStateException – if Cipher object is not in valid state./**
     * Ensures that Cipher is in a valid state for update() and doFinal()
     * calls - should be initialized and in ENCRYPT_MODE or DECRYPT_MODE.
     * @throws IllegalStateException if Cipher object is not in valid state.
     */
    private void checkCipherState() {
        if (!(this instanceof NullCipher)) {
            if (!initialized) {
                throw new IllegalStateException("Cipher not initialized");
            }
            if ((opmode != Cipher.ENCRYPT_MODE) &&
                (opmode != Cipher.DECRYPT_MODE)) {
                throw new IllegalStateException("Cipher not initialized " +
                                                "for encryption/decryption");
            }
        }
    }

    
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
The bytes in the input buffer are processed, and the
result is stored in a new buffer.
If input has a length of zero, this method returns
null.
Params:
input – the input buffer
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
Returns:
the new buffer with the result, or null if the underlying
cipher is a block cipher and the input data is too short to result in a
new block./**
     * Continues a multiple-part encryption or decryption operation
     * (depending on how this cipher was initialized), processing another data
     * part.
     *
     * <p>The bytes in the <code>input</code> buffer are processed, and the
     * result is stored in a new buffer.
     *
     * <p>If <code>input</code> has a length of zero, this method returns
     * <code>null</code>.
     *
     * @param input the input buffer
     *
     * @return the new buffer with the result, or null if the underlying
     * cipher is a block cipher and the input data is too short to result in a
     * new block.
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     */
    public final byte[] update(byte[] input) {
        checkCipherState();

        // Input sanity check
        if (input == null) {
            throw new IllegalArgumentException("Null input buffer");
        }

        chooseFirstProvider();
        if (input.length == 0) {
            return null;
        }
        return spi.engineUpdate(input, 0, input.length);
    }

    
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
The first inputLen bytes in the input
buffer, starting at inputOffset inclusive, are processed,
and the result is stored in a new buffer.
If inputLen is zero, this method returns
null.
Params:
input – the input buffer
inputOffset – the offset in input where the input
starts
inputLen – the input length
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
Returns:
the new buffer with the result, or null if the underlying
cipher is a block cipher and the input data is too short to result in a
new block./**
     * Continues a multiple-part encryption or decryption operation
     * (depending on how this cipher was initialized), processing another data
     * part.
     *
     * <p>The first <code>inputLen</code> bytes in the <code>input</code>
     * buffer, starting at <code>inputOffset</code> inclusive, are processed,
     * and the result is stored in a new buffer.
     *
     * <p>If <code>inputLen</code> is zero, this method returns
     * <code>null</code>.
     *
     * @param input the input buffer
     * @param inputOffset the offset in <code>input</code> where the input
     * starts
     * @param inputLen the input length
     *
     * @return the new buffer with the result, or null if the underlying
     * cipher is a block cipher and the input data is too short to result in a
     * new block.
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     */
    public final byte[] update(byte[] input, int inputOffset, int inputLen) {
        checkCipherState();

        // Input sanity check
        if (input == null || inputOffset < 0
            || inputLen > (input.length - inputOffset) || inputLen < 0) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        if (inputLen == 0) {
            return null;
        }
        return spi.engineUpdate(input, inputOffset, inputLen);
    }

    
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
The first inputLen bytes in the input
buffer, starting at inputOffset inclusive, are processed,
and the result is stored in the output buffer.
If the output buffer is too small to hold the result,
a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
If inputLen is zero, this method returns
a length of zero.
Note: this method should be copy-safe, which means the
input and output buffers can reference
the same byte array and no unprocessed input data is overwritten
when the result is copied into the output buffer.
Params:
input – the input buffer
inputOffset – the offset in input where the input
starts
inputLen – the input length
output – the buffer for the result
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
ShortBufferException – if the given output buffer is too small
to hold the result
Returns:
the number of bytes stored in output/**
     * Continues a multiple-part encryption or decryption operation
     * (depending on how this cipher was initialized), processing another data
     * part.
     *
     * <p>The first <code>inputLen</code> bytes in the <code>input</code>
     * buffer, starting at <code>inputOffset</code> inclusive, are processed,
     * and the result is stored in the <code>output</code> buffer.
     *
     * <p>If the <code>output</code> buffer is too small to hold the result,
     * a <code>ShortBufferException</code> is thrown. In this case, repeat this
     * call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>If <code>inputLen</code> is zero, this method returns
     * a length of zero.
     *
     * <p>Note: this method should be copy-safe, which means the
     * <code>input</code> and <code>output</code> buffers can reference
     * the same byte array and no unprocessed input data is overwritten
     * when the result is copied into the output buffer.
     *
     * @param input the input buffer
     * @param inputOffset the offset in <code>input</code> where the input
     * starts
     * @param inputLen the input length
     * @param output the buffer for the result
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception ShortBufferException if the given output buffer is too small
     * to hold the result
     */
    public final int update(byte[] input, int inputOffset, int inputLen,
                            byte[] output)
            throws ShortBufferException {
        checkCipherState();

        // Input sanity check
        if (input == null || inputOffset < 0
            || inputLen > (input.length - inputOffset) || inputLen < 0) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        if (inputLen == 0) {
            return 0;
        }
        return spi.engineUpdate(input, inputOffset, inputLen,
                                      output, 0);
    }

    
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
The first inputLen bytes in the input
buffer, starting at inputOffset inclusive, are processed,
and the result is stored in the output buffer, starting at
outputOffset inclusive.
If the output buffer is too small to hold the result,
a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
If inputLen is zero, this method returns
a length of zero.
Note: this method should be copy-safe, which means the
input and output buffers can reference
the same byte array and no unprocessed input data is overwritten
when the result is copied into the output buffer.
Params:
input – the input buffer
inputOffset – the offset in input where the input
starts
inputLen – the input length
output – the buffer for the result
outputOffset – the offset in output where the result
is stored
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
ShortBufferException – if the given output buffer is too small
to hold the result
Returns:
the number of bytes stored in output/**
     * Continues a multiple-part encryption or decryption operation
     * (depending on how this cipher was initialized), processing another data
     * part.
     *
     * <p>The first <code>inputLen</code> bytes in the <code>input</code>
     * buffer, starting at <code>inputOffset</code> inclusive, are processed,
     * and the result is stored in the <code>output</code> buffer, starting at
     * <code>outputOffset</code> inclusive.
     *
     * <p>If the <code>output</code> buffer is too small to hold the result,
     * a <code>ShortBufferException</code> is thrown. In this case, repeat this
     * call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>If <code>inputLen</code> is zero, this method returns
     * a length of zero.
     *
     * <p>Note: this method should be copy-safe, which means the
     * <code>input</code> and <code>output</code> buffers can reference
     * the same byte array and no unprocessed input data is overwritten
     * when the result is copied into the output buffer.
     *
     * @param input the input buffer
     * @param inputOffset the offset in <code>input</code> where the input
     * starts
     * @param inputLen the input length
     * @param output the buffer for the result
     * @param outputOffset the offset in <code>output</code> where the result
     * is stored
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception ShortBufferException if the given output buffer is too small
     * to hold the result
     */
    public final int update(byte[] input, int inputOffset, int inputLen,
                            byte[] output, int outputOffset)
            throws ShortBufferException {
        checkCipherState();

        // Input sanity check
        if (input == null || inputOffset < 0
            || inputLen > (input.length - inputOffset) || inputLen < 0
            || outputOffset < 0) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        if (inputLen == 0) {
            return 0;
        }
        return spi.engineUpdate(input, inputOffset, inputLen,
                                      output, outputOffset);
    }

    
Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.
All input.remaining() bytes starting at
input.position() are processed. The result is stored
in the output buffer.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed. The output buffer's
position will have advanced by n, where n is the value returned
by this method; the output buffer's limit will not have changed.
If output.remaining() bytes are insufficient to
hold the result, a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
Note: this method should be copy-safe, which means the
input and output buffers can reference
the same block of memory and no unprocessed input data is overwritten
when the result is copied into the output buffer.
Params:
input – the input ByteBuffer
output – the output ByteByffer
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalArgumentException – if input and output are the
  same object
ReadOnlyBufferException – if the output buffer is read-only
ShortBufferException – if there is insufficient space in the
output buffer
Returns:
the number of bytes stored in output
Since:
1.5/**
     * Continues a multiple-part encryption or decryption operation
     * (depending on how this cipher was initialized), processing another data
     * part.
     *
     * <p>All <code>input.remaining()</code> bytes starting at
     * <code>input.position()</code> are processed. The result is stored
     * in the output buffer.
     * Upon return, the input buffer's position will be equal
     * to its limit; its limit will not have changed. The output buffer's
     * position will have advanced by n, where n is the value returned
     * by this method; the output buffer's limit will not have changed.
     *
     * <p>If <code>output.remaining()</code> bytes are insufficient to
     * hold the result, a <code>ShortBufferException</code> is thrown.
     * In this case, repeat this call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>Note: this method should be copy-safe, which means the
     * <code>input</code> and <code>output</code> buffers can reference
     * the same block of memory and no unprocessed input data is overwritten
     * when the result is copied into the output buffer.
     *
     * @param input the input ByteBuffer
     * @param output the output ByteByffer
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalArgumentException if input and output are the
     *   same object
     * @exception ReadOnlyBufferException if the output buffer is read-only
     * @exception ShortBufferException if there is insufficient space in the
     * output buffer
     * @since 1.5
     */
    public final int update(ByteBuffer input, ByteBuffer output)
            throws ShortBufferException {
        checkCipherState();

        if ((input == null) || (output == null)) {
            throw new IllegalArgumentException("Buffers must not be null");
        }
        if (input == output) {
            throw new IllegalArgumentException("Input and output buffers must "
                + "not be the same object, consider using buffer.duplicate()");
        }
        if (output.isReadOnly()) {
            throw new ReadOnlyBufferException();
        }

        chooseFirstProvider();
        return spi.engineUpdate(input, output);
    }

    
Finishes a multiple-part encryption or decryption operation, depending
on how this cipher was initialized.
Input data that may have been buffered during a previous
update operation is processed, with padding (if requested)
being applied.
The result is stored in a new buffer.
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the new buffer with the result/**
     * Finishes a multiple-part encryption or decryption operation, depending
     * on how this cipher was initialized.
     *
     * <p>Input data that may have been buffered during a previous
     * <code>update</code> operation is processed, with padding (if requested)
     * being applied.
     * The result is stored in a new buffer.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * @return the new buffer with the result
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     */
    public final byte[] doFinal()
            throws IllegalBlockSizeException, BadPaddingException {
        checkCipherState();

        chooseFirstProvider();
        return spi.engineDoFinal(null, 0, 0);
    }

    
Finishes a multiple-part encryption or decryption operation, depending
on how this cipher was initialized.
Input data that may have been buffered during a previous
update operation is processed, with padding (if requested)
being applied.
The result is stored in the output buffer, starting at
outputOffset inclusive.
If the output buffer is too small to hold the result,
a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Params:
output – the buffer for the result
outputOffset – the offset in output where the result
is stored
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
ShortBufferException – if the given output buffer is too small
to hold the result
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the number of bytes stored in output/**
     * Finishes a multiple-part encryption or decryption operation, depending
     * on how this cipher was initialized.
     *
     * <p>Input data that may have been buffered during a previous
     * <code>update</code> operation is processed, with padding (if requested)
     * being applied.
     * The result is stored in the <code>output</code> buffer, starting at
     * <code>outputOffset</code> inclusive.
     *
     * <p>If the <code>output</code> buffer is too small to hold the result,
     * a <code>ShortBufferException</code> is thrown. In this case, repeat this
     * call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * @param output the buffer for the result
     * @param outputOffset the offset in <code>output</code> where the result
     * is stored
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception ShortBufferException if the given output buffer is too small
     * to hold the result
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     */
    public final int doFinal(byte[] output, int outputOffset)
            throws IllegalBlockSizeException, ShortBufferException,
               BadPaddingException {
        checkCipherState();

        // Input sanity check
        if ((output == null) || (outputOffset < 0)) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        return spi.engineDoFinal(null, 0, 0, output, outputOffset);
    }

    
Encrypts or decrypts data in a single-part operation, or finishes a
multiple-part operation. The data is encrypted or decrypted,
depending on how this cipher was initialized.
The bytes in the input buffer, and any input bytes that
may have been buffered during a previous update operation,
are processed, with padding (if requested) being applied.
The result is stored in a new buffer.
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Params:
input – the input buffer
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the new buffer with the result/**
     * Encrypts or decrypts data in a single-part operation, or finishes a
     * multiple-part operation. The data is encrypted or decrypted,
     * depending on how this cipher was initialized.
     *
     * <p>The bytes in the <code>input</code> buffer, and any input bytes that
     * may have been buffered during a previous <code>update</code> operation,
     * are processed, with padding (if requested) being applied.
     * The result is stored in a new buffer.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * @param input the input buffer
     *
     * @return the new buffer with the result
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     */
    public final byte[] doFinal(byte[] input)
            throws IllegalBlockSizeException, BadPaddingException {
        checkCipherState();

        // Input sanity check
        if (input == null) {
            throw new IllegalArgumentException("Null input buffer");
        }

        chooseFirstProvider();
        return spi.engineDoFinal(input, 0, input.length);
    }

    
Encrypts or decrypts data in a single-part operation, or finishes a
multiple-part operation. The data is encrypted or decrypted,
depending on how this cipher was initialized.
The first inputLen bytes in the input
buffer, starting at inputOffset inclusive, and any input
bytes that may have been buffered during a previous update
operation, are processed, with padding (if requested) being applied.
The result is stored in a new buffer.
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Params:
input – the input buffer
inputOffset – the offset in input where the input
starts
inputLen – the input length
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the new buffer with the result/**
     * Encrypts or decrypts data in a single-part operation, or finishes a
     * multiple-part operation. The data is encrypted or decrypted,
     * depending on how this cipher was initialized.
     *
     * <p>The first <code>inputLen</code> bytes in the <code>input</code>
     * buffer, starting at <code>inputOffset</code> inclusive, and any input
     * bytes that may have been buffered during a previous <code>update</code>
     * operation, are processed, with padding (if requested) being applied.
     * The result is stored in a new buffer.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * @param input the input buffer
     * @param inputOffset the offset in <code>input</code> where the input
     * starts
     * @param inputLen the input length
     *
     * @return the new buffer with the result
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     */
    public final byte[] doFinal(byte[] input, int inputOffset, int inputLen)
            throws IllegalBlockSizeException, BadPaddingException {
        checkCipherState();

        // Input sanity check
        if (input == null || inputOffset < 0
            || inputLen > (input.length - inputOffset) || inputLen < 0) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        return spi.engineDoFinal(input, inputOffset, inputLen);
    }

    
Encrypts or decrypts data in a single-part operation, or finishes a
multiple-part operation. The data is encrypted or decrypted,
depending on how this cipher was initialized.
The first inputLen bytes in the input
buffer, starting at inputOffset inclusive, and any input
bytes that may have been buffered during a previous update
operation, are processed, with padding (if requested) being applied.
The result is stored in the output buffer.
If the output buffer is too small to hold the result,
a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Note: this method should be copy-safe, which means the
input and output buffers can reference
the same byte array and no unprocessed input data is overwritten
when the result is copied into the output buffer.
Params:
input – the input buffer
inputOffset – the offset in input where the input
starts
inputLen – the input length
output – the buffer for the result
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
ShortBufferException – if the given output buffer is too small
to hold the result
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the number of bytes stored in output/**
     * Encrypts or decrypts data in a single-part operation, or finishes a
     * multiple-part operation. The data is encrypted or decrypted,
     * depending on how this cipher was initialized.
     *
     * <p>The first <code>inputLen</code> bytes in the <code>input</code>
     * buffer, starting at <code>inputOffset</code> inclusive, and any input
     * bytes that may have been buffered during a previous <code>update</code>
     * operation, are processed, with padding (if requested) being applied.
     * The result is stored in the <code>output</code> buffer.
     *
     * <p>If the <code>output</code> buffer is too small to hold the result,
     * a <code>ShortBufferException</code> is thrown. In this case, repeat this
     * call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * <p>Note: this method should be copy-safe, which means the
     * <code>input</code> and <code>output</code> buffers can reference
     * the same byte array and no unprocessed input data is overwritten
     * when the result is copied into the output buffer.
     *
     * @param input the input buffer
     * @param inputOffset the offset in <code>input</code> where the input
     * starts
     * @param inputLen the input length
     * @param output the buffer for the result
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception ShortBufferException if the given output buffer is too small
     * to hold the result
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     */
    public final int doFinal(byte[] input, int inputOffset, int inputLen,
                             byte[] output)
            throws ShortBufferException, IllegalBlockSizeException,
            BadPaddingException {
        checkCipherState();

        // Input sanity check
        if (input == null || inputOffset < 0
            || inputLen > (input.length - inputOffset) || inputLen < 0) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        return spi.engineDoFinal(input, inputOffset, inputLen,
                                       output, 0);
    }

    
Encrypts or decrypts data in a single-part operation, or finishes a
multiple-part operation. The data is encrypted or decrypted,
depending on how this cipher was initialized.
The first inputLen bytes in the input
buffer, starting at inputOffset inclusive, and any input
bytes that may have been buffered during a previous
update operation, are processed, with padding
(if requested) being applied.
The result is stored in the output buffer, starting at
outputOffset inclusive.
If the output buffer is too small to hold the result,
a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Note: this method should be copy-safe, which means the
input and output buffers can reference
the same byte array and no unprocessed input data is overwritten
when the result is copied into the output buffer.
Params:
input – the input buffer
inputOffset – the offset in input where the input
starts
inputLen – the input length
output – the buffer for the result
outputOffset – the offset in output where the result
is stored
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
ShortBufferException – if the given output buffer is too small
to hold the result
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the number of bytes stored in output/**
     * Encrypts or decrypts data in a single-part operation, or finishes a
     * multiple-part operation. The data is encrypted or decrypted,
     * depending on how this cipher was initialized.
     *
     * <p>The first <code>inputLen</code> bytes in the <code>input</code>
     * buffer, starting at <code>inputOffset</code> inclusive, and any input
     * bytes that may have been buffered during a previous
     * <code>update</code> operation, are processed, with padding
     * (if requested) being applied.
     * The result is stored in the <code>output</code> buffer, starting at
     * <code>outputOffset</code> inclusive.
     *
     * <p>If the <code>output</code> buffer is too small to hold the result,
     * a <code>ShortBufferException</code> is thrown. In this case, repeat this
     * call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * <p>Note: this method should be copy-safe, which means the
     * <code>input</code> and <code>output</code> buffers can reference
     * the same byte array and no unprocessed input data is overwritten
     * when the result is copied into the output buffer.
     *
     * @param input the input buffer
     * @param inputOffset the offset in <code>input</code> where the input
     * starts
     * @param inputLen the input length
     * @param output the buffer for the result
     * @param outputOffset the offset in <code>output</code> where the result
     * is stored
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception ShortBufferException if the given output buffer is too small
     * to hold the result
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     */
    public final int doFinal(byte[] input, int inputOffset, int inputLen,
                             byte[] output, int outputOffset)
            throws ShortBufferException, IllegalBlockSizeException,
            BadPaddingException {
        checkCipherState();

        // Input sanity check
        if (input == null || inputOffset < 0
            || inputLen > (input.length - inputOffset) || inputLen < 0
            || outputOffset < 0) {
            throw new IllegalArgumentException("Bad arguments");
        }

        chooseFirstProvider();
        return spi.engineDoFinal(input, inputOffset, inputLen,
                                       output, outputOffset);
    }

    
Encrypts or decrypts data in a single-part operation, or finishes a
multiple-part operation. The data is encrypted or decrypted,
depending on how this cipher was initialized.
All input.remaining() bytes starting at
input.position() are processed. The result is stored
in the output buffer.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed. The output buffer's
position will have advanced by n, where n is the value returned
by this method; the output buffer's limit will not have changed.
If output.remaining() bytes are insufficient to
hold the result, a ShortBufferException is thrown. In this case, repeat this call with a larger output buffer. Use getOutputSize to determine how big the output buffer should be. 
Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to init.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
init) more data.
Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.
Note: this method should be copy-safe, which means the
input and output buffers can reference
the same byte array and no unprocessed input data is overwritten
when the result is copied into the output buffer.
Params:
input – the input ByteBuffer
output – the output ByteBuffer
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized)
IllegalArgumentException – if input and output are the
  same object
ReadOnlyBufferException – if the output buffer is read-only
IllegalBlockSizeException – if this cipher is a block cipher,
no padding has been requested (only in encryption mode), and the total
input length of the data processed by this cipher is not a multiple of
block size; or if this encryption algorithm is unable to
process the input data provided.
ShortBufferException – if there is insufficient space in the
output buffer
BadPaddingException – if this cipher is in decryption mode,
and (un)padding has been requested, but the decrypted data is not
bounded by the appropriate padding bytes
Returns:
the number of bytes stored in output
Since:
1.5/**
     * Encrypts or decrypts data in a single-part operation, or finishes a
     * multiple-part operation. The data is encrypted or decrypted,
     * depending on how this cipher was initialized.
     *
     * <p>All <code>input.remaining()</code> bytes starting at
     * <code>input.position()</code> are processed. The result is stored
     * in the output buffer.
     * Upon return, the input buffer's position will be equal
     * to its limit; its limit will not have changed. The output buffer's
     * position will have advanced by n, where n is the value returned
     * by this method; the output buffer's limit will not have changed.
     *
     * <p>If <code>output.remaining()</code> bytes are insufficient to
     * hold the result, a <code>ShortBufferException</code> is thrown.
     * In this case, repeat this call with a larger output buffer. Use
     * {@link #getOutputSize(int) getOutputSize} to determine how big
     * the output buffer should be.
     *
     * <p>Upon finishing, this method resets this cipher object to the state
     * it was in when previously initialized via a call to <code>init</code>.
     * That is, the object is reset and available to encrypt or decrypt
     * (depending on the operation mode that was specified in the call to
     * <code>init</code>) more data.
     *
     * <p>Note: if any exception is thrown, this cipher object may need to
     * be reset before it can be used again.
     *
     * <p>Note: this method should be copy-safe, which means the
     * <code>input</code> and <code>output</code> buffers can reference
     * the same byte array and no unprocessed input data is overwritten
     * when the result is copied into the output buffer.
     *
     * @param input the input ByteBuffer
     * @param output the output ByteBuffer
     *
     * @return the number of bytes stored in <code>output</code>
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized)
     * @exception IllegalArgumentException if input and output are the
     *   same object
     * @exception ReadOnlyBufferException if the output buffer is read-only
     * @exception IllegalBlockSizeException if this cipher is a block cipher,
     * no padding has been requested (only in encryption mode), and the total
     * input length of the data processed by this cipher is not a multiple of
     * block size; or if this encryption algorithm is unable to
     * process the input data provided.
     * @exception ShortBufferException if there is insufficient space in the
     * output buffer
     * @exception BadPaddingException if this cipher is in decryption mode,
     * and (un)padding has been requested, but the decrypted data is not
     * bounded by the appropriate padding bytes
     * @since 1.5
     */
    public final int doFinal(ByteBuffer input, ByteBuffer output)
            throws ShortBufferException, IllegalBlockSizeException,
            BadPaddingException {
        checkCipherState();

        if ((input == null) || (output == null)) {
            throw new IllegalArgumentException("Buffers must not be null");
        }
        if (input == output) {
            throw new IllegalArgumentException("Input and output buffers must "
                + "not be the same object, consider using buffer.duplicate()");
        }
        if (output.isReadOnly()) {
            throw new ReadOnlyBufferException();
        }

        chooseFirstProvider();
        return spi.engineDoFinal(input, output);
    }

    
Wrap a key.
Params:
key – the key to be wrapped.
Throws:
IllegalStateException – if this cipher is in a wrong
state (e.g., has not been initialized).
IllegalBlockSizeException – if this cipher is a block
cipher, no padding has been requested, and the length of the
encoding of the key to be wrapped is not a
multiple of the block size.
InvalidKeyException – if it is impossible or unsafe to
wrap the key with this cipher (e.g., a hardware protected key is
being passed to a software-only cipher).
Returns:
the wrapped key./**
     * Wrap a key.
     *
     * @param key the key to be wrapped.
     *
     * @return the wrapped key.
     *
     * @exception IllegalStateException if this cipher is in a wrong
     * state (e.g., has not been initialized).
     *
     * @exception IllegalBlockSizeException if this cipher is a block
     * cipher, no padding has been requested, and the length of the
     * encoding of the key to be wrapped is not a
     * multiple of the block size.
     *
     * @exception InvalidKeyException if it is impossible or unsafe to
     * wrap the key with this cipher (e.g., a hardware protected key is
     * being passed to a software-only cipher).
     */
    public final byte[] wrap(Key key)
            throws IllegalBlockSizeException, InvalidKeyException {
        if (!(this instanceof NullCipher)) {
            if (!initialized) {
                throw new IllegalStateException("Cipher not initialized");
            }
            if (opmode != Cipher.WRAP_MODE) {
                throw new IllegalStateException("Cipher not initialized " +
                                                "for wrapping keys");
            }
        }

        chooseFirstProvider();
        return spi.engineWrap(key);
    }

    
Unwrap a previously wrapped key.
Params:
wrappedKey – the key to be unwrapped.
wrappedKeyAlgorithm – the algorithm associated with the wrapped
key.
wrappedKeyType – the type of the wrapped key. This must be one of
SECRET_KEY, PRIVATE_KEY, or
PUBLIC_KEY.
Throws:
IllegalStateException – if this cipher is in a wrong state
(e.g., has not been initialized).
NoSuchAlgorithmException – if no installed providers
can create keys of type wrappedKeyType for the
wrappedKeyAlgorithm.
InvalidKeyException – if wrappedKey does not
represent a wrapped key of type wrappedKeyType for
the wrappedKeyAlgorithm.
Returns:
the unwrapped key./**
     * Unwrap a previously wrapped key.
     *
     * @param wrappedKey the key to be unwrapped.
     *
     * @param wrappedKeyAlgorithm the algorithm associated with the wrapped
     * key.
     *
     * @param wrappedKeyType the type of the wrapped key. This must be one of
     * <code>SECRET_KEY</code>, <code>PRIVATE_KEY</code>, or
     * <code>PUBLIC_KEY</code>.
     *
     * @return the unwrapped key.
     *
     * @exception IllegalStateException if this cipher is in a wrong state
     * (e.g., has not been initialized).
     *
     * @exception NoSuchAlgorithmException if no installed providers
     * can create keys of type <code>wrappedKeyType</code> for the
     * <code>wrappedKeyAlgorithm</code>.
     *
     * @exception InvalidKeyException if <code>wrappedKey</code> does not
     * represent a wrapped key of type <code>wrappedKeyType</code> for
     * the <code>wrappedKeyAlgorithm</code>.
     */
    public final Key unwrap(byte[] wrappedKey,
                            String wrappedKeyAlgorithm,
                            int wrappedKeyType)
            throws InvalidKeyException, NoSuchAlgorithmException {

        if (!(this instanceof NullCipher)) {
            if (!initialized) {
                throw new IllegalStateException("Cipher not initialized");
            }
            if (opmode != Cipher.UNWRAP_MODE) {
                throw new IllegalStateException("Cipher not initialized " +
                                                "for unwrapping keys");
            }
        }
        if ((wrappedKeyType != SECRET_KEY) &&
            (wrappedKeyType != PRIVATE_KEY) &&
            (wrappedKeyType != PUBLIC_KEY)) {
            throw new InvalidParameterException("Invalid key type");
        }

        chooseFirstProvider();
        return spi.engineUnwrap(wrappedKey,
                                      wrappedKeyAlgorithm,
                                      wrappedKeyType);
    }

    private AlgorithmParameterSpec getAlgorithmParameterSpec(
                                      AlgorithmParameters params)
            throws InvalidParameterSpecException {
        if (params == null) {
            return null;
        }

        String alg = params.getAlgorithm().toUpperCase(Locale.ENGLISH);

        if (alg.equalsIgnoreCase("RC2")) {
            return params.getParameterSpec(RC2ParameterSpec.class);
        }

        if (alg.equalsIgnoreCase("RC5")) {
            return params.getParameterSpec(RC5ParameterSpec.class);
        }

        if (alg.startsWith("PBE")) {
            return params.getParameterSpec(PBEParameterSpec.class);
        }

        if (alg.startsWith("DES")) {
            return params.getParameterSpec(IvParameterSpec.class);
        }
        return null;
    }

    private static CryptoPermission getConfiguredPermission(
            String transformation) throws NullPointerException,
            NoSuchAlgorithmException {
        if (transformation == null) throw new NullPointerException();
        String[] parts = tokenizeTransformation(transformation);
        return JceSecurityManager.INSTANCE.getCryptoPermission(parts[0]);
    }

    
Returns the maximum key length for the specified transformation
according to the installed JCE jurisdiction policy files. If
JCE unlimited strength jurisdiction policy files are installed,
Integer.MAX_VALUE will be returned.
For more information on default key size in JCE jurisdiction
policy files, please see Appendix E in the

Java Cryptography Architecture Reference Guide.
Params:
transformation – the cipher transformation.
Throws:
NullPointerException – if transformation is null.
NoSuchAlgorithmException – if transformation
is not a valid transformation, i.e. in the form of "algorithm" or
"algorithm/mode/padding".
Returns:
the maximum key length in bits or Integer.MAX_VALUE.
Since:
1.5/**
     * Returns the maximum key length for the specified transformation
     * according to the installed JCE jurisdiction policy files. If
     * JCE unlimited strength jurisdiction policy files are installed,
     * Integer.MAX_VALUE will be returned.
     * For more information on default key size in JCE jurisdiction
     * policy files, please see Appendix E in the
     * <a href=
     *   "{@docRoot}/../technotes/guides/security/crypto/CryptoSpec.html#AppE">
     * Java Cryptography Architecture Reference Guide</a>.
     *
     * @param transformation the cipher transformation.
     * @return the maximum key length in bits or Integer.MAX_VALUE.
     * @exception NullPointerException if <code>transformation</code> is null.
     * @exception NoSuchAlgorithmException if <code>transformation</code>
     * is not a valid transformation, i.e. in the form of "algorithm" or
     * "algorithm/mode/padding".
     * @since 1.5
     */
    public static final int getMaxAllowedKeyLength(String transformation)
            throws NoSuchAlgorithmException {
        CryptoPermission cp = getConfiguredPermission(transformation);
        return cp.getMaxKeySize();
    }

    
Returns an AlgorithmParameterSpec object which contains
the maximum cipher parameter value according to the
jurisdiction policy file. If JCE unlimited strength jurisdiction
policy files are installed or there is no maximum limit on the
parameters for the specified transformation in the policy file,
null will be returned.
Params:
transformation – the cipher transformation.
Throws:
NullPointerException – if transformation
is null.
NoSuchAlgorithmException – if transformation
is not a valid transformation, i.e. in the form of "algorithm" or
"algorithm/mode/padding".
Returns:
an AlgorithmParameterSpec which holds the maximum
value or null.
Since:
1.5/**
     * Returns an AlgorithmParameterSpec object which contains
     * the maximum cipher parameter value according to the
     * jurisdiction policy file. If JCE unlimited strength jurisdiction
     * policy files are installed or there is no maximum limit on the
     * parameters for the specified transformation in the policy file,
     * null will be returned.
     *
     * @param transformation the cipher transformation.
     * @return an AlgorithmParameterSpec which holds the maximum
     * value or null.
     * @exception NullPointerException if <code>transformation</code>
     * is null.
     * @exception NoSuchAlgorithmException if <code>transformation</code>
     * is not a valid transformation, i.e. in the form of "algorithm" or
     * "algorithm/mode/padding".
     * @since 1.5
     */
    public static final AlgorithmParameterSpec getMaxAllowedParameterSpec(
            String transformation) throws NoSuchAlgorithmException {
        CryptoPermission cp = getConfiguredPermission(transformation);
        return cp.getAlgorithmParameterSpec();
    }
}