https://openjdk.java.net/ 
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 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * under the terms of the GNU General Public License version 2 only, as
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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
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 *
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package java.security.cert;

import java.math.BigInteger;
import java.security.*;
import java.security.spec.*;
import java.util.Collection;
import java.util.Date;
import java.util.List;
import javax.security.auth.x500.X500Principal;

import sun.security.x509.X509CertImpl;
import sun.security.util.SignatureUtil;



Abstract class for X.509 certificates. This provides a standard
way to access all the attributes of an X.509 certificate.


In June of 1996, the basic X.509 v3 format was completed by
ISO/IEC and ANSI X9, which is described below in ASN.1:

Certificate  ::=  SEQUENCE  {
    tbsCertificate       TBSCertificate,
    signatureAlgorithm   AlgorithmIdentifier,
    signature            BIT STRING  }




These certificates are widely used to support authentication and
other functionality in Internet security systems. Common applications
include Privacy Enhanced Mail (PEM), Transport Layer Security (SSL),
code signing for trusted software distribution, and Secure Electronic
Transactions (SET).


These certificates are managed and vouched for by Certificate
Authorities (CAs). CAs are services which create certificates by
placing data in the X.509 standard format and then digitally signing
that data. CAs act as trusted third parties, making introductions
between principals who have no direct knowledge of each other.
CA certificates are either signed by themselves, or by some other
CA such as a "root" CA.


More information can be found in
RFC 5280: Internet X.509
Public Key Infrastructure Certificate and CRL Profile.

 The ASN.1 definition of tbsCertificate is: 
TBSCertificate  ::=  SEQUENCE  {
    version         [0]  EXPLICIT Version DEFAULT v1,
    serialNumber         CertificateSerialNumber,
    signature            AlgorithmIdentifier,
    issuer               Name,
    validity             Validity,
    subject              Name,
    subjectPublicKeyInfo SubjectPublicKeyInfo,
    issuerUniqueID  [1]  IMPLICIT UniqueIdentifier OPTIONAL,
                         -- If present, version must be v2 or v3
    subjectUniqueID [2]  IMPLICIT UniqueIdentifier OPTIONAL,
                         -- If present, version must be v2 or v3
    extensions      [3]  EXPLICIT Extensions OPTIONAL
                         -- If present, version must be v3
    }




Certificates are instantiated using a certificate factory. The following is
an example of how to instantiate an X.509 certificate:

try (InputStream inStream = new FileInputStream("fileName-of-cert")) {
    CertificateFactory cf = CertificateFactory.getInstance("X.509");
    X509Certificate cert = (X509Certificate)cf.generateCertificate(inStream);
}



Author:Hemma Prafullchandra
See Also:
Since:1.2
/**
 * <p>
 * Abstract class for X.509 certificates. This provides a standard
 * way to access all the attributes of an X.509 certificate.
 * <p>
 * In June of 1996, the basic X.509 v3 format was completed by
 * ISO/IEC and ANSI X9, which is described below in ASN.1:
 * <pre>
 * Certificate  ::=  SEQUENCE  {
 *     tbsCertificate       TBSCertificate,
 *     signatureAlgorithm   AlgorithmIdentifier,
 *     signature            BIT STRING  }
 * </pre>
 * <p>
 * These certificates are widely used to support authentication and
 * other functionality in Internet security systems. Common applications
 * include Privacy Enhanced Mail (PEM), Transport Layer Security (SSL),
 * code signing for trusted software distribution, and Secure Electronic
 * Transactions (SET).
 * <p>
 * These certificates are managed and vouched for by <em>Certificate
 * Authorities</em> (CAs). CAs are services which create certificates by
 * placing data in the X.509 standard format and then digitally signing
 * that data. CAs act as trusted third parties, making introductions
 * between principals who have no direct knowledge of each other.
 * CA certificates are either signed by themselves, or by some other
 * CA such as a "root" CA.
 * <p>
 * More information can be found in
 * <a href="http://tools.ietf.org/html/rfc5280">RFC 5280: Internet X.509
 * Public Key Infrastructure Certificate and CRL Profile</a>.
 * <p>
 * The ASN.1 definition of {@code tbsCertificate} is:
 * <pre>
 * TBSCertificate  ::=  SEQUENCE  {
 *     version         [0]  EXPLICIT Version DEFAULT v1,
 *     serialNumber         CertificateSerialNumber,
 *     signature            AlgorithmIdentifier,
 *     issuer               Name,
 *     validity             Validity,
 *     subject              Name,
 *     subjectPublicKeyInfo SubjectPublicKeyInfo,
 *     issuerUniqueID  [1]  IMPLICIT UniqueIdentifier OPTIONAL,
 *                          -- If present, version must be v2 or v3
 *     subjectUniqueID [2]  IMPLICIT UniqueIdentifier OPTIONAL,
 *                          -- If present, version must be v2 or v3
 *     extensions      [3]  EXPLICIT Extensions OPTIONAL
 *                          -- If present, version must be v3
 *     }
 * </pre>
 * <p>
 * Certificates are instantiated using a certificate factory. The following is
 * an example of how to instantiate an X.509 certificate:
 * <pre>
 * try (InputStream inStream = new FileInputStream("fileName-of-cert")) {
 *     CertificateFactory cf = CertificateFactory.getInstance("X.509");
 *     X509Certificate cert = (X509Certificate)cf.generateCertificate(inStream);
 * }
 * </pre>
 *
 * @author Hemma Prafullchandra
 * @since 1.2
 *
 *
 * @see Certificate
 * @see CertificateFactory
 * @see X509Extension
 */

public abstract class X509Certificate extends Certificate
implements X509Extension {

    private static final long serialVersionUID = -2491127588187038216L;

    private transient X500Principal subjectX500Principal, issuerX500Principal;

    
Constructor for X.509 certificates.

/**
     * Constructor for X.509 certificates.
     */
    protected X509Certificate() {
        super("X.509");
    }

    
Checks that the certificate is currently valid. It is if
the current date and time are within the validity period given in the
certificate.


The validity period consists of two date/time values:
the first and last dates (and times) on which the certificate
is valid. It is defined in
ASN.1 as:

validity             Validity
Validity ::= SEQUENCE {
    notBefore      CertificateValidityDate,
    notAfter       CertificateValidityDate }
CertificateValidityDate ::= CHOICE {
    utcTime        UTCTime,
    generalTime    GeneralizedTime }



Throws:
/**
     * Checks that the certificate is currently valid. It is if
     * the current date and time are within the validity period given in the
     * certificate.
     * <p>
     * The validity period consists of two date/time values:
     * the first and last dates (and times) on which the certificate
     * is valid. It is defined in
     * ASN.1 as:
     * <pre>
     * validity             Validity
     *
     * Validity ::= SEQUENCE {
     *     notBefore      CertificateValidityDate,
     *     notAfter       CertificateValidityDate }
     *
     * CertificateValidityDate ::= CHOICE {
     *     utcTime        UTCTime,
     *     generalTime    GeneralizedTime }
     * </pre>
     *
     * @exception CertificateExpiredException if the certificate has expired.
     * @exception CertificateNotYetValidException if the certificate is not
     * yet valid.
     */
    public abstract void checkValidity()
        throws CertificateExpiredException, CertificateNotYetValidException;

    
Checks that the given date is within the certificate's
validity period. In other words, this determines whether the
certificate would be valid at the given date/time.

Params:
  • date – the Date to check against to see if this certificate
       is valid at that date/time.
Throws:
See Also:
/**
     * Checks that the given date is within the certificate's
     * validity period. In other words, this determines whether the
     * certificate would be valid at the given date/time.
     *
     * @param date the Date to check against to see if this certificate
     *        is valid at that date/time.
     *
     * @exception CertificateExpiredException if the certificate has expired
     * with respect to the {@code date} supplied.
     * @exception CertificateNotYetValidException if the certificate is not
     * yet valid with respect to the {@code date} supplied.
     *
     * @see #checkValidity()
     */
    public abstract void checkValidity(Date date)
        throws CertificateExpiredException, CertificateNotYetValidException;

    
Gets the version (version number) value from the certificate. The ASN.1 definition for this is: 
version  [0] EXPLICIT Version DEFAULT v1
Version ::=  INTEGER  {  v1(0), v2(1), v3(2)  }



Returns:the version number, i.e. 1, 2 or 3.
/**
     * Gets the {@code version} (version number) value from the
     * certificate.
     * The ASN.1 definition for this is:
     * <pre>
     * version  [0] EXPLICIT Version DEFAULT v1
     *
     * Version ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
     * </pre>
     * @return the version number, i.e. 1, 2 or 3.
     */
    public abstract int getVersion();

    
Gets the serialNumber value from the certificate. The serial number is an integer assigned by the certification authority to each certificate. It must be unique for each certificate issued by a given CA (i.e., the issuer name and serial number identify a unique certificate). The ASN.1 definition for this is: 
serialNumber     CertificateSerialNumber
CertificateSerialNumber  ::=  INTEGER



Returns:the serial number.
/**
     * Gets the {@code serialNumber} value from the certificate.
     * The serial number is an integer assigned by the certification
     * authority to each certificate. It must be unique for each
     * certificate issued by a given CA (i.e., the issuer name and
     * serial number identify a unique certificate).
     * The ASN.1 definition for this is:
     * <pre>
     * serialNumber     CertificateSerialNumber
     *
     * CertificateSerialNumber  ::=  INTEGER
     * </pre>
     *
     * @return the serial number.
     */
    public abstract BigInteger getSerialNumber();

    
Denigrated, replaced by getIssuerX500Principal(). This method returns the issuer as an implementation specific Principal object, which should not be relied upon by portable code. 
 Gets the issuer (issuer distinguished name) value from the certificate. The issuer name identifies the entity that signed (and issued) the certificate. 
The issuer name field contains an
X.500 distinguished name (DN).
The ASN.1 definition for this is:

issuer    Name
Name ::= CHOICE { RDNSequence }
RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
RelativeDistinguishedName ::=
    SET OF AttributeValueAssertion
AttributeValueAssertion ::= SEQUENCE {
                              AttributeType,
                              AttributeValue }
AttributeType ::= OBJECT IDENTIFIER
AttributeValue ::= ANY

 The Name describes a hierarchical name composed of attributes, such as country name, and corresponding values, such as US. The type of the AttributeValue component is determined by the AttributeType; in general it will be a directoryString. A directoryString is usually one of PrintableString, TeletexString or UniversalString. 
Returns:a Principal whose name is the issuer distinguished name.
/**
     * <strong>Denigrated</strong>, replaced by {@linkplain
     * #getIssuerX500Principal()}. This method returns the {@code issuer}
     * as an implementation specific Principal object, which should not be
     * relied upon by portable code.
     *
     * <p>
     * Gets the {@code issuer} (issuer distinguished name) value from
     * the certificate. The issuer name identifies the entity that signed (and
     * issued) the certificate.
     *
     * <p>The issuer name field contains an
     * X.500 distinguished name (DN).
     * The ASN.1 definition for this is:
     * <pre>
     * issuer    Name
     *
     * Name ::= CHOICE { RDNSequence }
     * RDNSequence ::= SEQUENCE OF RelativeDistinguishedName
     * RelativeDistinguishedName ::=
     *     SET OF AttributeValueAssertion
     *
     * AttributeValueAssertion ::= SEQUENCE {
     *                               AttributeType,
     *                               AttributeValue }
     * AttributeType ::= OBJECT IDENTIFIER
     * AttributeValue ::= ANY
     * </pre>
     * The {@code Name} describes a hierarchical name composed of
     * attributes,
     * such as country name, and corresponding values, such as US.
     * The type of the {@code AttributeValue} component is determined by
     * the {@code AttributeType}; in general it will be a
     * {@code directoryString}. A {@code directoryString} is usually
     * one of {@code PrintableString},
     * {@code TeletexString} or {@code UniversalString}.
     *
     * @return a Principal whose name is the issuer distinguished name.
     */
    public abstract Principal getIssuerDN();

    
Returns the issuer (issuer distinguished name) value from the certificate as an X500Principal. 

It is recommended that subclasses override this method.

Returns:an X500Principal representing the issuer distinguished name
Since:1.4
/**
     * Returns the issuer (issuer distinguished name) value from the
     * certificate as an {@code X500Principal}.
     * <p>
     * It is recommended that subclasses override this method.
     *
     * @return an {@code X500Principal} representing the issuer
     *          distinguished name
     * @since 1.4
     */
    public X500Principal getIssuerX500Principal() {
        if (issuerX500Principal == null) {
            issuerX500Principal = X509CertImpl.getIssuerX500Principal(this);
        }
        return issuerX500Principal;
    }

    
Denigrated, replaced by getSubjectX500Principal(). This method returns the subject as an implementation specific Principal object, which should not be relied upon by portable code. 
 Gets the subject (subject distinguished name) value from the certificate. If the subject value is empty, then the getName() method of the returned Principal object returns an empty string (""). 
 The ASN.1 definition for this is:

subject    Name



See getIssuerDN for Name and other relevant definitions. 
Returns:a Principal whose name is the subject name.
/**
     * <strong>Denigrated</strong>, replaced by {@linkplain
     * #getSubjectX500Principal()}. This method returns the {@code subject}
     * as an implementation specific Principal object, which should not be
     * relied upon by portable code.
     *
     * <p>
     * Gets the {@code subject} (subject distinguished name) value
     * from the certificate.  If the {@code subject} value is empty,
     * then the {@code getName()} method of the returned
     * {@code Principal} object returns an empty string ("").
     *
     * <p> The ASN.1 definition for this is:
     * <pre>
     * subject    Name
     * </pre>
     *
     * <p>See {@link #getIssuerDN() getIssuerDN} for {@code Name}
     * and other relevant definitions.
     *
     * @return a Principal whose name is the subject name.
     */
    public abstract Principal getSubjectDN();

    
Returns the subject (subject distinguished name) value from the certificate as an X500Principal. If the subject value is empty, then the getName() method of the returned X500Principal object returns an empty string (""). 

It is recommended that subclasses override this method.

Returns:an X500Principal representing the subject distinguished name
Since:1.4
/**
     * Returns the subject (subject distinguished name) value from the
     * certificate as an {@code X500Principal}.  If the subject value
     * is empty, then the {@code getName()} method of the returned
     * {@code X500Principal} object returns an empty string ("").
     * <p>
     * It is recommended that subclasses override this method.
     *
     * @return an {@code X500Principal} representing the subject
     *          distinguished name
     * @since 1.4
     */
    public X500Principal getSubjectX500Principal() {
        if (subjectX500Principal == null) {
            subjectX500Principal = X509CertImpl.getSubjectX500Principal(this);
        }
        return subjectX500Principal;
    }

    
Gets the notBefore date from the validity period of the certificate. The relevant ASN.1 definitions are: 
validity             Validity
Validity ::= SEQUENCE {
    notBefore      CertificateValidityDate,
    notAfter       CertificateValidityDate }
CertificateValidityDate ::= CHOICE {
    utcTime        UTCTime,
    generalTime    GeneralizedTime }



See Also:
Returns:the start date of the validity period.
/**
     * Gets the {@code notBefore} date from the validity period of
     * the certificate.
     * The relevant ASN.1 definitions are:
     * <pre>
     * validity             Validity
     *
     * Validity ::= SEQUENCE {
     *     notBefore      CertificateValidityDate,
     *     notAfter       CertificateValidityDate }
     *
     * CertificateValidityDate ::= CHOICE {
     *     utcTime        UTCTime,
     *     generalTime    GeneralizedTime }
     * </pre>
     *
     * @return the start date of the validity period.
     * @see #checkValidity
     */
    public abstract Date getNotBefore();

    
Gets the notAfter date from the validity period of the certificate. See getNotBefore for relevant ASN.1 definitions. 
See Also:
Returns:the end date of the validity period.
/**
     * Gets the {@code notAfter} date from the validity period of
     * the certificate. See {@link #getNotBefore() getNotBefore}
     * for relevant ASN.1 definitions.
     *
     * @return the end date of the validity period.
     * @see #checkValidity
     */
    public abstract Date getNotAfter();

    
Gets the DER-encoded certificate information, the tbsCertificate from this certificate. This can be used to verify the signature independently. 
Throws:
Returns:the DER-encoded certificate information.
/**
     * Gets the DER-encoded certificate information, the
     * {@code tbsCertificate} from this certificate.
     * This can be used to verify the signature independently.
     *
     * @return the DER-encoded certificate information.
     * @exception CertificateEncodingException if an encoding error occurs.
     */
    public abstract byte[] getTBSCertificate()
        throws CertificateEncodingException;

    
Gets the signature value (the raw signature bits) from the certificate. The ASN.1 definition for this is: 
signature     BIT STRING



Returns:the signature.
/**
     * Gets the {@code signature} value (the raw signature bits) from
     * the certificate.
     * The ASN.1 definition for this is:
     * <pre>
     * signature     BIT STRING
     * </pre>
     *
     * @return the signature.
     */
    public abstract byte[] getSignature();

    
Gets the signature algorithm name for the certificate
signature algorithm. An example is the string "SHA256withRSA".
The ASN.1 definition for this is:

signatureAlgorithm   AlgorithmIdentifier
AlgorithmIdentifier  ::=  SEQUENCE  {
    algorithm               OBJECT IDENTIFIER,
    parameters              ANY DEFINED BY algorithm OPTIONAL  }
                            -- contains a value of the type
                            -- registered for use with the
                            -- algorithm object identifier value



The algorithm name is determined from the algorithm OID string. 
Returns:the signature algorithm name.
/**
     * Gets the signature algorithm name for the certificate
     * signature algorithm. An example is the string "SHA256withRSA".
     * The ASN.1 definition for this is:
     * <pre>
     * signatureAlgorithm   AlgorithmIdentifier
     *
     * AlgorithmIdentifier  ::=  SEQUENCE  {
     *     algorithm               OBJECT IDENTIFIER,
     *     parameters              ANY DEFINED BY algorithm OPTIONAL  }
     *                             -- contains a value of the type
     *                             -- registered for use with the
     *                             -- algorithm object identifier value
     * </pre>
     *
     * <p>The algorithm name is determined from the {@code algorithm}
     * OID string.
     *
     * @return the signature algorithm name.
     */
    public abstract String getSigAlgName();

    
Gets the signature algorithm OID string from the certificate.
An OID is represented by a set of nonnegative whole numbers separated
by periods.
For example, the string "1.2.840.10040.4.3" identifies the SHA-1
with DSA signature algorithm defined in
RFC 3279: Algorithms and
Identifiers for the Internet X.509 Public Key Infrastructure Certificate
and CRL Profile.

See getSigAlgName for relevant ASN.1 definitions. 
Returns:the signature algorithm OID string.
/**
     * Gets the signature algorithm OID string from the certificate.
     * An OID is represented by a set of nonnegative whole numbers separated
     * by periods.
     * For example, the string "1.2.840.10040.4.3" identifies the SHA-1
     * with DSA signature algorithm defined in
     * <a href="http://www.ietf.org/rfc/rfc3279.txt">RFC 3279: Algorithms and
     * Identifiers for the Internet X.509 Public Key Infrastructure Certificate
     * and CRL Profile</a>.
     *
     * <p>See {@link #getSigAlgName() getSigAlgName} for
     * relevant ASN.1 definitions.
     *
     * @return the signature algorithm OID string.
     */
    public abstract String getSigAlgOID();

    
Gets the DER-encoded signature algorithm parameters from this certificate's signature algorithm. In most cases, the signature algorithm parameters are null; the parameters are usually supplied with the certificate's public key. If access to individual parameter values is needed then use AlgorithmParameters and instantiate with the name returned by getSigAlgName. 
See getSigAlgName for relevant ASN.1 definitions. 
Returns:the DER-encoded signature algorithm parameters, or
        null if no parameters are present.
/**
     * Gets the DER-encoded signature algorithm parameters from this
     * certificate's signature algorithm. In most cases, the signature
     * algorithm parameters are null; the parameters are usually
     * supplied with the certificate's public key.
     * If access to individual parameter values is needed then use
     * {@link java.security.AlgorithmParameters AlgorithmParameters}
     * and instantiate with the name returned by
     * {@link #getSigAlgName() getSigAlgName}.
     *
     * <p>See {@link #getSigAlgName() getSigAlgName} for
     * relevant ASN.1 definitions.
     *
     * @return the DER-encoded signature algorithm parameters, or
     *         null if no parameters are present.
     */
    public abstract byte[] getSigAlgParams();

    
Gets the issuerUniqueID value from the certificate. The issuer unique identifier is present in the certificate to handle the possibility of reuse of issuer names over time. RFC 5280 recommends that names not be reused and that conforming certificates not make use of unique identifiers. Applications conforming to that profile should be capable of parsing unique identifiers and making comparisons. 
The ASN.1 definition for this is:

issuerUniqueID  [1]  IMPLICIT UniqueIdentifier OPTIONAL
UniqueIdentifier  ::=  BIT STRING



Returns:the issuer unique identifier or null if it is not
present in the certificate.
/**
     * Gets the {@code issuerUniqueID} value from the certificate.
     * The issuer unique identifier is present in the certificate
     * to handle the possibility of reuse of issuer names over time.
     * RFC 5280 recommends that names not be reused and that
     * conforming certificates not make use of unique identifiers.
     * Applications conforming to that profile should be capable of
     * parsing unique identifiers and making comparisons.
     *
     * <p>The ASN.1 definition for this is:
     * <pre>
     * issuerUniqueID  [1]  IMPLICIT UniqueIdentifier OPTIONAL
     *
     * UniqueIdentifier  ::=  BIT STRING
     * </pre>
     *
     * @return the issuer unique identifier or null if it is not
     * present in the certificate.
     */
    public abstract boolean[] getIssuerUniqueID();

    
Gets the subjectUniqueID value from the certificate. 
The ASN.1 definition for this is:

subjectUniqueID  [2]  IMPLICIT UniqueIdentifier OPTIONAL
UniqueIdentifier  ::=  BIT STRING



Returns:the subject unique identifier or null if it is not
present in the certificate.
/**
     * Gets the {@code subjectUniqueID} value from the certificate.
     *
     * <p>The ASN.1 definition for this is:
     * <pre>
     * subjectUniqueID  [2]  IMPLICIT UniqueIdentifier OPTIONAL
     *
     * UniqueIdentifier  ::=  BIT STRING
     * </pre>
     *
     * @return the subject unique identifier or null if it is not
     * present in the certificate.
     */
    public abstract boolean[] getSubjectUniqueID();

    
Gets a boolean array representing bits of the KeyUsage extension, (OID = 2.5.29.15). The key usage extension defines the purpose (e.g., encipherment, signature, certificate signing) of the key contained in the certificate. The ASN.1 definition for this is: 
KeyUsage ::= BIT STRING {
    digitalSignature        (0),
    nonRepudiation          (1),
    keyEncipherment         (2),
    dataEncipherment        (3),
    keyAgreement            (4),
    keyCertSign             (5),
    cRLSign                 (6),
    encipherOnly            (7),
    decipherOnly            (8) }


RFC 5280 recommends that when used, this be marked
as a critical extension.

Returns:the KeyUsage extension of this certificate, represented as
an array of booleans. The order of KeyUsage values in the array is
the same as in the above ASN.1 definition. The array will contain a
value for each KeyUsage defined above. If the KeyUsage list encoded
in the certificate is longer than the above list, it will not be
truncated. Returns null if this certificate does not
contain a KeyUsage extension.
/**
     * Gets a boolean array representing bits of
     * the {@code KeyUsage} extension, (OID = 2.5.29.15).
     * The key usage extension defines the purpose (e.g., encipherment,
     * signature, certificate signing) of the key contained in the
     * certificate.
     * The ASN.1 definition for this is:
     * <pre>
     * KeyUsage ::= BIT STRING {
     *     digitalSignature        (0),
     *     nonRepudiation          (1),
     *     keyEncipherment         (2),
     *     dataEncipherment        (3),
     *     keyAgreement            (4),
     *     keyCertSign             (5),
     *     cRLSign                 (6),
     *     encipherOnly            (7),
     *     decipherOnly            (8) }
     * </pre>
     * RFC 5280 recommends that when used, this be marked
     * as a critical extension.
     *
     * @return the KeyUsage extension of this certificate, represented as
     * an array of booleans. The order of KeyUsage values in the array is
     * the same as in the above ASN.1 definition. The array will contain a
     * value for each KeyUsage defined above. If the KeyUsage list encoded
     * in the certificate is longer than the above list, it will not be
     * truncated. Returns null if this certificate does not
     * contain a KeyUsage extension.
     */
    public abstract boolean[] getKeyUsage();

    
Gets an unmodifiable list of Strings representing the OBJECT IDENTIFIERs of the ExtKeyUsageSyntax field of the extended key usage extension, (OID = 2.5.29.37). It indicates one or more purposes for which the certified public key may be used, in addition to or in place of the basic purposes indicated in the key usage extension field. The ASN.1 definition for this is: 
ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
KeyPurposeId ::= OBJECT IDENTIFIER


Key purposes may be defined by any organization with a
need. Object identifiers used to identify key purposes shall be
assigned in accordance with IANA or ITU-T Rec. X.660 |
ISO/IEC/ITU 9834-1.

 This method was added to version 1.4 of the Java 2 Platform Standard Edition. In order to maintain backwards compatibility with existing service providers, this method is not abstract and it provides a default implementation. Subclasses should override this method with a correct implementation. 
Throws:
Returns:the ExtendedKeyUsage extension of this certificate,
        as an unmodifiable list of object identifiers represented
        as Strings. Returns null if this certificate does not
        contain an ExtendedKeyUsage extension.
Since:1.4
/**
     * Gets an unmodifiable list of Strings representing the OBJECT
     * IDENTIFIERs of the {@code ExtKeyUsageSyntax} field of the
     * extended key usage extension, (OID = 2.5.29.37).  It indicates
     * one or more purposes for which the certified public key may be
     * used, in addition to or in place of the basic purposes
     * indicated in the key usage extension field.  The ASN.1
     * definition for this is:
     * <pre>
     * ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
     *
     * KeyPurposeId ::= OBJECT IDENTIFIER
     * </pre>
     *
     * Key purposes may be defined by any organization with a
     * need. Object identifiers used to identify key purposes shall be
     * assigned in accordance with IANA or ITU-T Rec. X.660 |
     * ISO/IEC/ITU 9834-1.
     * <p>
     * This method was added to version 1.4 of the Java 2 Platform Standard
     * Edition. In order to maintain backwards compatibility with existing
     * service providers, this method is not {@code abstract}
     * and it provides a default implementation. Subclasses
     * should override this method with a correct implementation.
     *
     * @return the ExtendedKeyUsage extension of this certificate,
     *         as an unmodifiable list of object identifiers represented
     *         as Strings. Returns null if this certificate does not
     *         contain an ExtendedKeyUsage extension.
     * @throws CertificateParsingException if the extension cannot be decoded
     * @since 1.4
     */
    public List<String> getExtendedKeyUsage() throws CertificateParsingException {
        return X509CertImpl.getExtendedKeyUsage(this);
    }

    
Gets the certificate constraints path length from the critical BasicConstraints extension, (OID = 2.5.29.19). 
 The basic constraints extension identifies whether the subject of the certificate is a Certificate Authority (CA) and how deep a certification path may exist through that CA. The pathLenConstraint field (see below) is meaningful only if cA is set to TRUE. In this case, it gives the maximum number of CA certificates that may follow this certificate in a certification path. A value of zero indicates that only an end-entity certificate may follow in the path. 

The ASN.1 definition for this is:

BasicConstraints ::= SEQUENCE {
    cA                  BOOLEAN DEFAULT FALSE,
    pathLenConstraint   INTEGER (0..MAX) OPTIONAL }



Returns:the value of pathLenConstraint if the BasicConstraints extension is present in the certificate and the subject of the certificate is a CA, otherwise -1. If the subject of the certificate is a CA and pathLenConstraint does not appear, Integer.MAX_VALUE is returned to indicate that there is no limit to the allowed length of the certification path.
/**
     * Gets the certificate constraints path length from the
     * critical {@code BasicConstraints} extension, (OID = 2.5.29.19).
     * <p>
     * The basic constraints extension identifies whether the subject
     * of the certificate is a Certificate Authority (CA) and
     * how deep a certification path may exist through that CA. The
     * {@code pathLenConstraint} field (see below) is meaningful
     * only if {@code cA} is set to TRUE. In this case, it gives the
     * maximum number of CA certificates that may follow this certificate in a
     * certification path. A value of zero indicates that only an end-entity
     * certificate may follow in the path.
     * <p>
     * The ASN.1 definition for this is:
     * <pre>
     * BasicConstraints ::= SEQUENCE {
     *     cA                  BOOLEAN DEFAULT FALSE,
     *     pathLenConstraint   INTEGER (0..MAX) OPTIONAL }
     * </pre>
     *
     * @return the value of {@code pathLenConstraint} if the
     * BasicConstraints extension is present in the certificate and the
     * subject of the certificate is a CA, otherwise -1.
     * If the subject of the certificate is a CA and
     * {@code pathLenConstraint} does not appear,
     * {@code Integer.MAX_VALUE} is returned to indicate that there is no
     * limit to the allowed length of the certification path.
     */
    public abstract int getBasicConstraints();

    
Gets an immutable collection of subject alternative names from the SubjectAltName extension, (OID = 2.5.29.17). 
 The ASN.1 definition of the SubjectAltName extension is: 
SubjectAltName ::= GeneralNames
GeneralNames :: = SEQUENCE SIZE (1..MAX) OF GeneralName
GeneralName ::= CHOICE {
     otherName                       [0]     OtherName,
     rfc822Name                      [1]     IA5String,
     dNSName                         [2]     IA5String,
     x400Address                     [3]     ORAddress,
     directoryName                   [4]     Name,
     ediPartyName                    [5]     EDIPartyName,
     uniformResourceIdentifier       [6]     IA5String,
     iPAddress                       [7]     OCTET STRING,
     registeredID                    [8]     OBJECT IDENTIFIER}



 If this certificate does not contain a SubjectAltName extension, null is returned. Otherwise, a Collection is returned with an entry representing each GeneralName included in the extension. Each entry is a List whose first entry is an Integer (the name type, 0-8) and whose second entry is a String or a byte array (the name, in string or ASN.1 DER encoded form, respectively). 

RFC 822, DNS, and URI names are returned as Strings, using the well-established string formats for those types (subject to the restrictions included in RFC 5280). IPv4 address names are returned using dotted quad notation. IPv6 address names are returned in the form "a1:a2:...:a8", where a1-a8 are hexadecimal values representing the eight 16-bit pieces of the address. OID names are returned as Strings represented as a series of nonnegative integers separated by periods. And directory names (distinguished names) are returned in 
RFC 2253 string format. No standard string format is
defined for otherNames, X.400 names, EDI party names, or any
other type of names. They are returned as byte arrays
containing the ASN.1 DER encoded form of the name.

 Note that the Collection returned may contain more than one name of the same type. Also, note that the returned Collection is immutable and any entries containing byte arrays are cloned to protect against subsequent modifications. 
 This method was added to version 1.4 of the Java 2 Platform Standard Edition. In order to maintain backwards compatibility with existing service providers, this method is not abstract and it provides a default implementation. Subclasses should override this method with a correct implementation. 
Throws:
Returns:an immutable Collection of subject alternative names (or null)
Since:1.4
/**
     * Gets an immutable collection of subject alternative names from the
     * {@code SubjectAltName} extension, (OID = 2.5.29.17).
     * <p>
     * The ASN.1 definition of the {@code SubjectAltName} extension is:
     * <pre>
     * SubjectAltName ::= GeneralNames
     *
     * GeneralNames :: = SEQUENCE SIZE (1..MAX) OF GeneralName
     *
     * GeneralName ::= CHOICE {
     *      otherName                       [0]     OtherName,
     *      rfc822Name                      [1]     IA5String,
     *      dNSName                         [2]     IA5String,
     *      x400Address                     [3]     ORAddress,
     *      directoryName                   [4]     Name,
     *      ediPartyName                    [5]     EDIPartyName,
     *      uniformResourceIdentifier       [6]     IA5String,
     *      iPAddress                       [7]     OCTET STRING,
     *      registeredID                    [8]     OBJECT IDENTIFIER}
     * </pre>
     * <p>
     * If this certificate does not contain a {@code SubjectAltName}
     * extension, {@code null} is returned. Otherwise, a
     * {@code Collection} is returned with an entry representing each
     * {@code GeneralName} included in the extension. Each entry is a
     * {@code List} whose first entry is an {@code Integer}
     * (the name type, 0-8) and whose second entry is a {@code String}
     * or a byte array (the name, in string or ASN.1 DER encoded form,
     * respectively).
     * <p>
     * <a href="http://www.ietf.org/rfc/rfc822.txt">RFC 822</a>, DNS, and URI
     * names are returned as {@code String}s,
     * using the well-established string formats for those types (subject to
     * the restrictions included in RFC 5280). IPv4 address names are
     * returned using dotted quad notation. IPv6 address names are returned
     * in the form "a1:a2:...:a8", where a1-a8 are hexadecimal values
     * representing the eight 16-bit pieces of the address. OID names are
     * returned as {@code String}s represented as a series of nonnegative
     * integers separated by periods. And directory names (distinguished names)
     * are returned in <a href="http://www.ietf.org/rfc/rfc2253.txt">
     * RFC 2253</a> string format. No standard string format is
     * defined for otherNames, X.400 names, EDI party names, or any
     * other type of names. They are returned as byte arrays
     * containing the ASN.1 DER encoded form of the name.
     * <p>
     * Note that the {@code Collection} returned may contain more
     * than one name of the same type. Also, note that the returned
     * {@code Collection} is immutable and any entries containing byte
     * arrays are cloned to protect against subsequent modifications.
     * <p>
     * This method was added to version 1.4 of the Java 2 Platform Standard
     * Edition. In order to maintain backwards compatibility with existing
     * service providers, this method is not {@code abstract}
     * and it provides a default implementation. Subclasses
     * should override this method with a correct implementation.
     *
     * @return an immutable {@code Collection} of subject alternative
     * names (or {@code null})
     * @throws CertificateParsingException if the extension cannot be decoded
     * @since 1.4
     */
    public Collection<List<?>> getSubjectAlternativeNames()
        throws CertificateParsingException {
        return X509CertImpl.getSubjectAlternativeNames(this);
    }

    
Gets an immutable collection of issuer alternative names from the IssuerAltName extension, (OID = 2.5.29.18). 
 The ASN.1 definition of the IssuerAltName extension is: 
IssuerAltName ::= GeneralNames

 The ASN.1 definition of GeneralNames is defined in getSubjectAlternativeNames. 
 If this certificate does not contain an IssuerAltName extension, null is returned. Otherwise, a Collection is returned with an entry representing each GeneralName included in the extension. Each entry is a List whose first entry is an Integer (the name type, 0-8) and whose second entry is a String or a byte array (the name, in string or ASN.1 DER encoded form, respectively). For more details about the formats used for each name type, see the getSubjectAlternativeNames method. 
 Note that the Collection returned may contain more than one name of the same type. Also, note that the returned Collection is immutable and any entries containing byte arrays are cloned to protect against subsequent modifications. 
 This method was added to version 1.4 of the Java 2 Platform Standard Edition. In order to maintain backwards compatibility with existing service providers, this method is not abstract and it provides a default implementation. Subclasses should override this method with a correct implementation. 
Throws:
Returns:an immutable Collection of issuer alternative names (or null)
Since:1.4
/**
     * Gets an immutable collection of issuer alternative names from the
     * {@code IssuerAltName} extension, (OID = 2.5.29.18).
     * <p>
     * The ASN.1 definition of the {@code IssuerAltName} extension is:
     * <pre>
     * IssuerAltName ::= GeneralNames
     * </pre>
     * The ASN.1 definition of {@code GeneralNames} is defined
     * in {@link #getSubjectAlternativeNames getSubjectAlternativeNames}.
     * <p>
     * If this certificate does not contain an {@code IssuerAltName}
     * extension, {@code null} is returned. Otherwise, a
     * {@code Collection} is returned with an entry representing each
     * {@code GeneralName} included in the extension. Each entry is a
     * {@code List} whose first entry is an {@code Integer}
     * (the name type, 0-8) and whose second entry is a {@code String}
     * or a byte array (the name, in string or ASN.1 DER encoded form,
     * respectively). For more details about the formats used for each
     * name type, see the {@code getSubjectAlternativeNames} method.
     * <p>
     * Note that the {@code Collection} returned may contain more
     * than one name of the same type. Also, note that the returned
     * {@code Collection} is immutable and any entries containing byte
     * arrays are cloned to protect against subsequent modifications.
     * <p>
     * This method was added to version 1.4 of the Java 2 Platform Standard
     * Edition. In order to maintain backwards compatibility with existing
     * service providers, this method is not {@code abstract}
     * and it provides a default implementation. Subclasses
     * should override this method with a correct implementation.
     *
     * @return an immutable {@code Collection} of issuer alternative
     * names (or {@code null})
     * @throws CertificateParsingException if the extension cannot be decoded
     * @since 1.4
     */
    public Collection<List<?>> getIssuerAlternativeNames()
        throws CertificateParsingException {
        return X509CertImpl.getIssuerAlternativeNames(this);
    }

    
Verifies that this certificate was signed using the private key that corresponds to the specified public key. This method uses the signature verification engine supplied by the specified provider. Note that the specified Provider object does not have to be registered in the provider list. This method was added to version 1.8 of the Java Platform Standard Edition. In order to maintain backwards compatibility with existing service providers, this method is not abstract and it provides a default implementation. 
Params:
  • key – the PublicKey used to carry out the verification.
  • sigProvider – the signature provider.
Throws:
Since:1.8
/**
     * Verifies that this certificate was signed using the
     * private key that corresponds to the specified public key.
     * This method uses the signature verification engine
     * supplied by the specified provider. Note that the specified
     * Provider object does not have to be registered in the provider list.
     *
     * This method was added to version 1.8 of the Java Platform Standard
     * Edition. In order to maintain backwards compatibility with existing
     * service providers, this method is not {@code abstract}
     * and it provides a default implementation.
     *
     * @param key the PublicKey used to carry out the verification.
     * @param sigProvider the signature provider.
     *
     * @exception NoSuchAlgorithmException on unsupported signature
     * algorithms.
     * @exception InvalidKeyException on incorrect key.
     * @exception SignatureException on signature errors.
     * @exception CertificateException on encoding errors.
     * @exception UnsupportedOperationException if the method is not supported
     * @since 1.8
     */
    public void verify(PublicKey key, Provider sigProvider)
        throws CertificateException, NoSuchAlgorithmException,
        InvalidKeyException, SignatureException {
        String sigName = getSigAlgName();
        Signature sig = (sigProvider == null)
            ? Signature.getInstance(sigName)
            : Signature.getInstance(sigName, sigProvider);

        try {
            SignatureUtil.initVerifyWithParam(sig, key,
                SignatureUtil.getParamSpec(sigName, getSigAlgParams()));
        } catch (ProviderException e) {
            throw new CertificateException(e.getMessage(), e.getCause());
        } catch (InvalidAlgorithmParameterException e) {
            throw new CertificateException(e);
        }

        byte[] tbsCert = getTBSCertificate();
        sig.update(tbsCert, 0, tbsCert.length);

        if (sig.verify(getSignature()) == false) {
            throw new SignatureException("Signature does not match.");
        }
    }
}