/*
 * =============================================================================
 * 
 *   Copyright (c) 2007-2010, The JASYPT team (http://www.jasypt.org)
 * 
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 * 
 *       http://www.apache.org/licenses/LICENSE-2.0
 * 
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 * 
 * =============================================================================
 */
package org.jasypt.encryption.pbe;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.security.Provider;

import org.jasypt.commons.CommonUtils;
import org.jasypt.encryption.pbe.config.PBEConfig;
import org.jasypt.exceptions.EncryptionInitializationException;
import org.jasypt.exceptions.EncryptionOperationNotPossibleException;
import org.jasypt.iv.IvGenerator;
import org.jasypt.salt.SaltGenerator;


 Standard implementation of the PBEBigDecimalEncryptor interface. This class lets the user specify the algorithm (and provider) to be used for encryption, the password to use, the number of hashing iterations and the salt generator that will be applied for obtaining the encryption key. 

Important: The size of the result of encrypting a number, depending
on the algorithm, may be much bigger (in bytes) than the size of the 
encrypted number itself. For example, encrypting a 4-byte integer can
result in an encrypted 16-byte number. This can lead the user into 
problems if the encrypted values are to be stored and not enough room 
has been provided.


This class is thread-safe.



Configuration


The algorithm, provider, password, key-obtention iterations and salt generator can take 
values in any of these ways:

  
Using its default values (except for password).
  
Setting a PBEConfig 
      object which provides new 
      configuration values.
  
Calling the corresponding setAlgorithm(...), 
      setProvider(...), setProviderName(...),
      setPassword(...), setKeyObtentionIterations(...) or
      setSaltGenerator(...) methods.

And the actual values to be used for initialization will be established
by applying the following priorities:

  
First, the default values are considered (except for password).
  
Then, if a PBEConfig 
      object has been set with
      setConfig(...), the non-null values returned by its
      getX() methods override the default values.
  
Finally, if the corresponding setX(...) method has been called
      on the encryptor itself for any of the configuration parameters, the 
      values set by these calls override all of the above.




Initialization


Before it is ready to encrypt, an object of this class has to be
initialized. Initialization happens:

  
When initialize() is called.
  
When encrypt(...) or decrypt(...) are called for the
      first time, if initialize() has not been called before.

Once an encryptor has been initialized, trying to
change its configuration will
result in an AlreadyInitializedException being thrown.



Usage


An encryptor may be used for:

  
Encrypting messages, by calling the encrypt(...) method.
  
Decrypting messages, by calling the decrypt(...) method.
 

If a random salt generator is used, two encryption results for 
the same message will always be different
(except in the case of random salt coincidence). This may enforce
security by difficulting brute force attacks on sets of data at a time
and forcing attackers to perform a brute force attack on each separate
piece of encrypted data.

     
To learn more about the mechanisms involved in encryption, read
PKCS #5: Password-Based Cryptography Standard.

Author:
Daniel Fernández
Since:
1.2/**
 * <p>
 * Standard implementation of the {@link PBEBigDecimalEncryptor} interface.
 * This class lets the user specify the algorithm (and provider) to be used for 
 * encryption, the password to use,
 * the number of hashing iterations and the salt generator
 * that will be applied for obtaining
 * the encryption key.
 * </p>
 * <p>
 * <b>Important</b>: The size of the result of encrypting a number, depending
 * on the algorithm, may be much bigger (in bytes) than the size of the 
 * encrypted number itself. For example, encrypting a 4-byte integer can
 * result in an encrypted 16-byte number. This can lead the user into 
 * problems if the encrypted values are to be stored and not enough room 
 * has been provided.
 * </p>
 * <p>
 * This class is <i>thread-safe</i>.
 * </p>
 * <p>
 * <br/><b><u>Configuration</u></b>
 * </p>
 * <p>
 * The algorithm, provider, password, key-obtention iterations and salt generator can take 
 * values in any of these ways:
 * <ul>
 *   <li>Using its default values (except for password).</li>
 *   <li>Setting a <tt>{@link org.jasypt.encryption.pbe.config.PBEConfig}</tt> 
 *       object which provides new 
 *       configuration values.</li>
 *   <li>Calling the corresponding <tt>setAlgorithm(...)</tt>, 
 *       <tt>setProvider(...)</tt>, <tt>setProviderName(...)</tt>,
 *       <tt>setPassword(...)</tt>, <tt>setKeyObtentionIterations(...)</tt> or
 *       <tt>setSaltGenerator(...)</tt> methods.</li>
 * </ul>
 * And the actual values to be used for initialization will be established
 * by applying the following priorities:
 * <ol>
 *   <li>First, the default values are considered (except for password).</li>
 *   <li>Then, if a <tt>{@link org.jasypt.encryption.pbe.config.PBEConfig}</tt> 
 *       object has been set with
 *       <tt>setConfig(...)</tt>, the non-null values returned by its
 *       <tt>getX()</tt> methods override the default values.</li>
 *   <li>Finally, if the corresponding <tt>setX(...)</tt> method has been called
 *       on the encryptor itself for any of the configuration parameters, the 
 *       values set by these calls override all of the above.</li>
 * </ol>
 * </p>
 * 
 * <p>
 * <br/><b><u>Initialization</u></b>
 * </p>
 * <p>
 * Before it is ready to encrypt, an object of this class has to be
 * <i>initialized</i>. Initialization happens:
 * <ul>
 *   <li>When <tt>initialize()</tt> is called.</li>
 *   <li>When <tt>encrypt(...)</tt> or <tt>decrypt(...)</tt> are called for the
 *       first time, if <tt>initialize()</tt> has not been called before.</li>
 * </ul>
 * Once an encryptor has been initialized, trying to
 * change its configuration will
 * result in an <tt>AlreadyInitializedException</tt> being thrown.
 * </p>
 * 
 * <p>
 * <br/><b><u>Usage</u></b>
 * </p>
 * <p>
 * An encryptor may be used for:
 * <ul>
 *   <li><i>Encrypting messages</i>, by calling the <tt>encrypt(...)</tt> method.</li>
 *   <li><i>Decrypting messages</i>, by calling the <tt>decrypt(...)</tt> method.</li> 
 * </ul>
 * <b>If a random salt generator is used, two encryption results for 
 * the same message will always be different
 * (except in the case of random salt coincidence)</b>. This may enforce
 * security by difficulting brute force attacks on sets of data at a time
 * and forcing attackers to perform a brute force attack on each separate
 * piece of encrypted data.
 * </p>
 * <p>     
 * To learn more about the mechanisms involved in encryption, read
 * <a href="http://www.rsasecurity.com/rsalabs/node.asp?id=2127" 
 * target="_blank">PKCS &#035;5: Password-Based Cryptography Standard</a>.
 * </p>
 * 
 * @since 1.2
 * 
 * @author Daniel Fern&aacute;ndez
 * 
 */
public final class StandardPBEBigDecimalEncryptor 
        implements PBEBigDecimalCleanablePasswordEncryptor {

    
    // The StandardPBEByteEncryptor that will be internally used.
    private final StandardPBEByteEncryptor byteEncryptor;

    
    
    
Creates a new instance of StandardPBEBigDecimalEncryptor.
/**
     * Creates a new instance of <tt>StandardPBEBigDecimalEncryptor</tt>.
     */
    public StandardPBEBigDecimalEncryptor() {
        super();
        this.byteEncryptor = new StandardPBEByteEncryptor();
    }


    
    /*
     * Creates a new instance of <tt>StandardPBEBigDecimalEncryptor</tt> using
     * the specified byte digester (constructor used for cloning)
     */
    private StandardPBEBigDecimalEncryptor(final StandardPBEByteEncryptor standardPBEByteEncryptor) {
        super();
        this.byteEncryptor = standardPBEByteEncryptor;
    }

    
    
    

Sets a PBEConfig object 
for the encryptor. If this config
object is set, it will be asked values for:


  
Algorithm
  
Security Provider (or provider name)
  
Password
  
Hashing iterations for obtaining the encryption key
  
Salt generator


The non-null values it returns will override the default ones, 
and will be overriden by any values specified with a setX
method.

Params:
config – the PBEConfig object to be used as the 
              source for configuration parameters./**
     * <p>
     * Sets a <tt>{@link org.jasypt.encryption.pbe.config.PBEConfig}</tt> object 
     * for the encryptor. If this config
     * object is set, it will be asked values for:
     * </p>
     * 
     * <ul>
     *   <li>Algorithm</li>
     *   <li>Security Provider (or provider name)</li>
     *   <li>Password</li>
     *   <li>Hashing iterations for obtaining the encryption key</li>
     *   <li>Salt generator</li>
     * </ul>
     * 
     * <p>
     * The non-null values it returns will override the default ones, 
     * <i>and will be overriden by any values specified with a <tt>setX</tt>
     * method</i>.
     * </p>
     * 
     * @param config the <tt>PBEConfig</tt> object to be used as the 
     *               source for configuration parameters.
     */
    public void setConfig(final PBEConfig config) {
        this.byteEncryptor.setConfig(config);
    }

    
    

Sets the algorithm to be used for encryption, like 
PBEWithMD5AndDES.


This algorithm has to be supported by your JCE provider (if you specify
one, or the default JVM provider if you don't) and, if it is supported,
you can also specify mode and padding for 
it, like ALGORITHM/MODE/PADDING.

Params:
algorithm – the name of the algorithm to be used./**
     * <p>
     * Sets the algorithm to be used for encryption, like 
     * <tt>PBEWithMD5AndDES</tt>.
     * </p>
     * <p>
     * This algorithm has to be supported by your JCE provider (if you specify
     * one, or the default JVM provider if you don't) and, if it is supported,
     * you can also specify <i>mode</i> and <i>padding</i> for 
     * it, like <tt>ALGORITHM/MODE/PADDING</tt>.
     * </p>
     * 
     * @param algorithm the name of the algorithm to be used.
     */
    public void setAlgorithm(final String algorithm) {
        this.byteEncryptor.setAlgorithm(algorithm);
    }

    
    

Sets the password to be used.


There is no default value for password, so not setting this parameter either from a PBEConfig object or from a call to setPassword will result in an
EncryptionInitializationException being thrown during initialization.

Params:
password – the password to be used./**
     * <p>
     * Sets the password to be used.
     * </p>
     * <p>
     * <b>There is no default value for password</b>, so not setting
     * this parameter either from a 
     * {@link org.jasypt.encryption.pbe.config.PBEConfig} object or from
     * a call to <tt>setPassword</tt> will result in an
     * EncryptionInitializationException being thrown during initialization.
     * </p>
     * 
     * @param password the password to be used.
     */
    public void setPassword(final String password) {
        this.byteEncryptor.setPassword(password);
    }
    
    
    

Sets the password to be used, as a char[].


This allows the password to be specified as a cleanable
char[] instead of a String, in extreme security conscious environments
in which no copy of the password as an immutable String should
be kept in memory.


Important: the array specified as a parameter WILL BE COPIED
in order to be stored as encryptor configuration. The caller of
this method will therefore be responsible for its cleaning (jasypt
will only clean the internally stored copy).


There is no default value for password, so not setting this parameter either from a PBEConfig object or from a call to setPassword will result in an
EncryptionInitializationException being thrown during initialization.

Params:
password – the password to be used.
Since:
1.8/**
     * <p>
     * Sets the password to be used, as a char[].
     * </p>
     * <p>
     * This allows the password to be specified as a <i>cleanable</i>
     * char[] instead of a String, in extreme security conscious environments
     * in which no copy of the password as an immutable String should
     * be kept in memory.
     * </p>
     * <p>
     * <b>Important</b>: the array specified as a parameter WILL BE COPIED
     * in order to be stored as encryptor configuration. The caller of
     * this method will therefore be responsible for its cleaning (jasypt
     * will only clean the internally stored copy).
     * </p>
     * <p>
     * <b>There is no default value for password</b>, so not setting
     * this parameter either from a 
     * {@link org.jasypt.encryption.pbe.config.PBEConfig} object or from
     * a call to <tt>setPassword</tt> will result in an
     * EncryptionInitializationException being thrown during initialization.
     * </p>
     * 
     * @since 1.8
     * 
     * @param password the password to be used.
     */
    public void setPasswordCharArray(char[] password) {
        this.byteEncryptor.setPasswordCharArray(password);
    }
    

    

Set the number of hashing iterations applied to obtain the
encryption key.


This mechanism is explained in 
PKCS #5: Password-Based Cryptography Standard.

Params:
keyObtentionIterations – the number of iterations/**
     * <p>
     * Set the number of hashing iterations applied to obtain the
     * encryption key.
     * </p>
     * <p>
     * This mechanism is explained in 
     * <a href="http://www.rsasecurity.com/rsalabs/node.asp?id=2127" 
     * target="_blank">PKCS &#035;5: Password-Based Cryptography Standard</a>.
     * </p>
     * 
     * @param keyObtentionIterations the number of iterations
     */
    public void setKeyObtentionIterations(final int keyObtentionIterations) {
        this.byteEncryptor.setKeyObtentionIterations(keyObtentionIterations);
    }

    
    
 Sets the salt generator to be used. If no salt generator is specified, an instance of RandomSaltGenerator will be used. 
Params:
saltGenerator – the salt generator to be used./**
     * <p>
     * Sets the salt generator to be used. If no salt generator is specified,
     * an instance of {@link org.jasypt.salt.RandomSaltGenerator} will be used. 
     * </p>
     * 
     * @param saltGenerator the salt generator to be used.
     */
    public void setSaltGenerator(final SaltGenerator saltGenerator) {
        this.byteEncryptor.setSaltGenerator(saltGenerator);
    }

    
 Sets the IV generator to be used. If no IV generator is specified, an instance of NoIvGenerator will be used. 
Params:
ivGenerator – the IV generator to be used./**
     * <p>
     * Sets the IV generator to be used. If no IV generator is specified,
     * an instance of {@link org.jasypt.iv.NoIvGenerator} will be used.
     * </p>
     *
     * @param ivGenerator the IV generator to be used.
     */
    public void setIvGenerator(final IvGenerator ivGenerator) {
        this.byteEncryptor.setIvGenerator(ivGenerator);
    }
    
    
    

Sets the name of the security provider to be asked for the
encryption algorithm. This security provider has to be registered 
beforehand at the JVM security framework. 

 The provider can also be set with the setProvider(Provider) method, in which case it will not be necessary neither registering the provider beforehand, nor calling this setProviderName(String) method to specify a provider name. 
 Note that a call to setProvider(Provider) overrides any value set by this method. 

If no provider name / provider is explicitly set, the default JVM
provider will be used.

Params:
providerName – the name of the security provider to be asked
                    for the encryption algorithm.
Since:
1.3/**
     * <p>
     * Sets the name of the security provider to be asked for the
     * encryption algorithm. This security provider has to be registered 
     * beforehand at the JVM security framework. 
     * </p>
     * <p>
     * The provider can also be set with the {@link #setProvider(Provider)}
     * method, in which case it will not be necessary neither registering
     * the provider beforehand,
     * nor calling this {@link #setProviderName(String)} method to specify
     * a provider name.
     * </p>
     * <p>
     * Note that a call to {@link #setProvider(Provider)} overrides any value 
     * set by this method.
     * </p>
     * <p>
     * If no provider name / provider is explicitly set, the default JVM
     * provider will be used.
     * </p>
     * 
     * @since 1.3
     * 
     * @param providerName the name of the security provider to be asked
     *                     for the encryption algorithm.
     */
    public void setProviderName(final String providerName) {
        this.byteEncryptor.setProviderName(providerName);
    }
    
    
    

Sets the security provider to be asked for the encryption algorithm.
The provider does not have to be registered at the security 
infrastructure beforehand, and its being used here will not result in
its being registered.

 If this method is called, calling setProviderName(String) becomes unnecessary. 

If no provider name / provider is explicitly set, the default JVM
provider will be used.

Params:
provider – the provider to be asked for the chosen algorithm
Since:
1.3/**
     * <p>
     * Sets the security provider to be asked for the encryption algorithm.
     * The provider does not have to be registered at the security 
     * infrastructure beforehand, and its being used here will not result in
     * its being registered.
     * </p>
     * <p>
     * If this method is called, calling {@link #setProviderName(String)}
     * becomes unnecessary.
     * </p>
     * <p>
     * If no provider name / provider is explicitly set, the default JVM
     * provider will be used.
     * </p>
     * 
     * @since 1.3
     * 
     * @param provider the provider to be asked for the chosen algorithm
     */
    public void setProvider(final Provider provider) {
        this.byteEncryptor.setProvider(provider);
    }

    

    


    
    
    
    
    /*
     * Clone this encryptor 'size' times and initialize it.
     * This encryptor will be at position 0 itself.
     * Clones will NOT be initialized.
     */
    synchronized StandardPBEBigDecimalEncryptor[] cloneAndInitializeEncryptor(final int size) {
        
        final StandardPBEByteEncryptor[] byteEncryptorClones =
            this.byteEncryptor.cloneAndInitializeEncryptor(size);
        
        final StandardPBEBigDecimalEncryptor[] clones = new StandardPBEBigDecimalEncryptor[size];
        
        clones[0] = this;
        
        for (int i = 1; i < size; i++) {
            clones[i] = new StandardPBEBigDecimalEncryptor(byteEncryptorClones[i]);
        }
        
        return clones;
        
    }
    
    
    

    

  Returns true if the encryptor has already been initialized, false if
  not.
 
  Initialization happens:


  
When initialize is called.
  
When encrypt or decrypt are called for the
      first time, if initialize has not been called before.


  Once an encryptor has been initialized, trying to
  change its configuration will
  result in an AlreadyInitializedException being thrown.

Returns:
true if the encryptor has already been initialized, false if
        not./**
     * <p>
     *   Returns true if the encryptor has already been initialized, false if
     *   not.<br/> 
     *   Initialization happens:
     * </p>
     * <ul>
     *   <li>When <tt>initialize</tt> is called.</li>
     *   <li>When <tt>encrypt</tt> or <tt>decrypt</tt> are called for the
     *       first time, if <tt>initialize</tt> has not been called before.</li>
     * </ul>
     * <p>
     *   Once an encryptor has been initialized, trying to
     *   change its configuration will
     *   result in an <tt>AlreadyInitializedException</tt> being thrown.
     * </p>
     * 
     * @return true if the encryptor has already been initialized, false if
     *         not.
     */
    public boolean isInitialized() {
        return this.byteEncryptor.isInitialized();
    }

    
    

Initialize the encryptor.


This operation will consist in determining the actual configuration 
values to be used, and then initializing the encryptor with them.


These values are decided by applying the following priorities:


  
First, the default values are considered (except for password).
  
  
Then, if a 
      PBEConfig 
      object has been set with
      setConfig, the non-null values returned by its
      getX methods override the default values.
  
Finally, if the corresponding setX method has been called
      on the encryptor itself for any of the configuration parameters, 
      the values set by these calls override all of the above.


  Once an encryptor has been initialized, trying to
  change its configuration will
  result in an AlreadyInitializedException being thrown.

Throws:
EncryptionInitializationException – if initialization could not
        be correctly done (for example, no password has been set)./**
     * <p>
     * Initialize the encryptor.
     * </p>
     * <p>
     * This operation will consist in determining the actual configuration 
     * values to be used, and then initializing the encryptor with them.
     * <br/>
     * These values are decided by applying the following priorities:
     * </p>
     * <ol>
     *   <li>First, the default values are considered (except for password).
     *   </li>
     *   <li>Then, if a 
     *       <tt>{@link org.jasypt.encryption.pbe.config.PBEConfig}</tt> 
     *       object has been set with
     *       <tt>setConfig</tt>, the non-null values returned by its
     *       <tt>getX</tt> methods override the default values.</li>
     *   <li>Finally, if the corresponding <tt>setX</tt> method has been called
     *       on the encryptor itself for any of the configuration parameters, 
     *       the values set by these calls override all of the above.</li>
     * </ol>
     * <p>
     *   Once an encryptor has been initialized, trying to
     *   change its configuration will
     *   result in an <tt>AlreadyInitializedException</tt> being thrown.
     * </p>
     * 
     * @throws EncryptionInitializationException if initialization could not
     *         be correctly done (for example, no password has been set).
     */
    public void initialize() {
        this.byteEncryptor.initialize();
    }
    
    
    

Encrypts a message using the specified configuration.


The resulting
BigDecimal will have the same scale as the original one (although the
total number of bytes will be higher).


Important: The size of the result of encrypting a number, depending
on the algorithm, may be much bigger (in bytes) than the size of the 
encrypted number itself. For example, encrypting a 4-byte integer can
result in an encrypted 16-byte number. This can lead the user into 
problems if the encrypted values are to be stored and not enough room 
has been provided.


The mechanisms applied to perform the encryption operation are described
in PKCS #5: Password-Based Cryptography Standard.


This encryptor uses a salt for each encryption
operation. The size of the salt depends on the algorithm
being used. This salt is used
for creating the encryption key and, if generated by a random generator,
it is also appended unencrypted at the beginning
of the results so that a decryption operation can be performed.


If a random salt generator is used, two encryption results for 
the same message will always be different
(except in the case of random salt coincidence). This may enforce
security by difficulting brute force attacks on sets of data at a time
and forcing attackers to perform a brute force attack on each separate
piece of encrypted data.

Params:
message – the BigDecimal message to be encrypted
Throws:
EncryptionOperationNotPossibleException – if the encryption 
        operation fails, ommitting any further information about the
        cause for security reasons.
EncryptionInitializationException – if initialization could not
        be correctly done (for example, no password has been set).
Returns:
the result of encryption/**
     * <p>
     * Encrypts a message using the specified configuration.
     * </p>
     * <p>
     * The resulting
     * BigDecimal will have the same scale as the original one (although the
     * total number of bytes will be higher).
     * </p>
     * <p>
     * <b>Important</b>: The size of the result of encrypting a number, depending
     * on the algorithm, may be much bigger (in bytes) than the size of the 
     * encrypted number itself. For example, encrypting a 4-byte integer can
     * result in an encrypted 16-byte number. This can lead the user into 
     * problems if the encrypted values are to be stored and not enough room 
     * has been provided.
     * </p>
     * <p>
     * The mechanisms applied to perform the encryption operation are described
     * in <a href="http://www.rsasecurity.com/rsalabs/node.asp?id=2127" 
     * target="_blank">PKCS &#035;5: Password-Based Cryptography Standard</a>.
     * </p>
     * <p>
     * This encryptor uses a salt for each encryption
     * operation. The size of the salt depends on the algorithm
     * being used. This salt is used
     * for creating the encryption key and, if generated by a random generator,
     * it is also appended unencrypted at the beginning
     * of the results so that a decryption operation can be performed.
     * </p>
     * <p>
     * <b>If a random salt generator is used, two encryption results for 
     * the same message will always be different
     * (except in the case of random salt coincidence)</b>. This may enforce
     * security by difficulting brute force attacks on sets of data at a time
     * and forcing attackers to perform a brute force attack on each separate
     * piece of encrypted data.
     * </p>
     * 
     * @param message the BigDecimal message to be encrypted
     * @return the result of encryption 
     * @throws EncryptionOperationNotPossibleException if the encryption 
     *         operation fails, ommitting any further information about the
     *         cause for security reasons.
     * @throws EncryptionInitializationException if initialization could not
     *         be correctly done (for example, no password has been set).
     */
    public BigDecimal encrypt(final BigDecimal message) {
        
        if (message == null) {
            return null;
        }
        
        try {
            
            // Get the scale of the decimal number
            final int scale = message.scale();
            
            // Get the number in binary form (without scale)
            final BigInteger unscaledMessage = message.unscaledValue();
            final byte[] messageBytes = unscaledMessage.toByteArray();
            
            // The StandardPBEByteEncryptor does its job.
            final byte[] encryptedMessage = this.byteEncryptor.encrypt(messageBytes);

            // The length of the encrypted message will be stored
            // with the result itself so that we can correctly rebuild
            // the complete byte array when decrypting (BigInteger will
            // ignore all "0x0" bytes in the leftmost side, and also "-0x1" 
            // in the leftmost side will be translated as signum).
            final byte[] encryptedMessageLengthBytes =
                NumberUtils.byteArrayFromInt(encryptedMessage.length);
            
            // Append the length bytes to the encrypted message
            final byte[] encryptionResult = 
                CommonUtils.appendArrays(encryptedMessage, encryptedMessageLengthBytes);

            // Finally, return a new number built from the encrypted bytes
            return new BigDecimal(new BigInteger(encryptionResult), scale);
        
        } catch (EncryptionInitializationException e) {
            throw e;
        } catch (EncryptionOperationNotPossibleException e) {
            throw e;
        } catch (Exception e) {
            // If encryption fails, it is more secure not to return any 
            // information about the cause in nested exceptions. Simply fail.
            throw new EncryptionOperationNotPossibleException();
        }
        
    }

    
    

Decrypts a message using the specified configuration.


The mechanisms applied to perform the decryption operation are described
in PKCS #5: Password-Based Cryptography Standard.


If a random salt generator is used, this decryption operation will
expect to find an unencrypted salt at the 
beginning of the encrypted input, so that the decryption operation can be
correctly performed (there is no other way of knowing it).

Params:
encryptedMessage – the BigDecimal message to be decrypted
Throws:
EncryptionOperationNotPossibleException – if the decryption 
        operation fails, ommitting any further information about the
        cause for security reasons.
EncryptionInitializationException – if initialization could not
        be correctly done (for example, no password has been set).
Returns:
the result of decryption/**
     * <p>
     * Decrypts a message using the specified configuration.
     * </p>
     * <p>
     * The mechanisms applied to perform the decryption operation are described
     * in <a href="http://www.rsasecurity.com/rsalabs/node.asp?id=2127" 
     * target="_blank">PKCS &#035;5: Password-Based Cryptography Standard</a>.
     * </p>
     * <p>
     * If a random salt generator is used, this decryption operation will
     * expect to find an unencrypted salt at the 
     * beginning of the encrypted input, so that the decryption operation can be
     * correctly performed (there is no other way of knowing it).
     * </p>
     * 
     * @param encryptedMessage the BigDecimal message to be decrypted
     * @return the result of decryption 
     * @throws EncryptionOperationNotPossibleException if the decryption 
     *         operation fails, ommitting any further information about the
     *         cause for security reasons.
     * @throws EncryptionInitializationException if initialization could not
     *         be correctly done (for example, no password has been set).
     */
    public BigDecimal decrypt(BigDecimal encryptedMessage) {
        
        if (encryptedMessage == null) {
            return null;
        }
        
        try {

            // Get the scale
            int scale = encryptedMessage.scale();
            
            // Get the number (unscaled) in binary form
            BigInteger unscaledEncryptedMessage = 
                encryptedMessage.unscaledValue();
            byte[] encryptedMessageBytes = 
                unscaledEncryptedMessage.toByteArray();

            // Process the encrypted byte array (check size, pad if needed...)
            encryptedMessageBytes = 
                NumberUtils.processBigIntegerEncryptedByteArray(
                        encryptedMessageBytes, encryptedMessage.signum());

            // Let the byte encyptor decrypt
            byte[] message = this.byteEncryptor.decrypt(encryptedMessageBytes);

            // Finally, return a new number built from the decrypted bytes
            return new BigDecimal(new BigInteger(message), scale);
        
        } catch (EncryptionInitializationException e) {
            throw e;
        } catch (EncryptionOperationNotPossibleException e) {
            throw e;
        } catch (Exception e) {
            // If decryption fails, it is more secure not to return any 
            // information about the cause in nested exceptions. Simply fail.
            throw new EncryptionOperationNotPossibleException();
        }

    }

    
}