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## java.security.cert
Class X509Certificate

    java.lang.Object
      |
      +--java.security.cert.Certificate
            |
            +--java.security.cert.X509Certificate

All Implemented Interfaces:
  Serializable, X509Extension

public abstract class X509Certificate
extends Certificate
implements X509Extension

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 2459, "Internet X.509 Public Key Infrastructure Certificate and CRL Profile" at http://www.ietf.org/rfc/rfc2459.txt .

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:

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

See Also:
  `Certificate`, `CertificateFactory`, `X509Extension`, Serialized Form

Inner classes inherited from class java.security.cert.Certificate
`Certificate.CertificateRep`

Constructor Summary
`protected` | `X509Certificate()` Constructor for X.509 certificates.

Method Summary
`abstract void` | `checkValidity()` Checks that the certificate is currently valid.
`abstract void` | `checkValidity(Date date)` Checks that the given date is within the certificate's validity period.
`abstract int` | `getBasicConstraints()` Gets the certificate constraints path length from the critical `BasicConstraints` extension, (OID = 2.5.29.19).
`abstract Principal` | `getIssuerDN()` Gets the `issuer` (issuer distinguished name) value from the certificate.
`abstract boolean[]` | `getIssuerUniqueID()` Gets the `issuerUniqueID` value from the certificate.
`abstract boolean[]` | `getKeyUsage()` Gets a boolean array representing bits of the `KeyUsage` extension, (OID = 2.5.29.15).
`abstract Date` | `getNotAfter()` Gets the `notAfter` date from the validity period of the certificate.
`abstract Date` | `getNotBefore()` Gets the `notBefore` date from the validity period of the certificate.
`abstract BigInteger` | `getSerialNumber()` Gets the `serialNumber` value from the certificate.
`abstract String` | `getSigAlgName()` Gets the signature algorithm name for the certificate signature algorithm.
`abstract String` | `getSigAlgOID()` Gets the signature algorithm OID string from the certificate.
`abstract byte[]` | `getSigAlgParams()` Gets the DER-encoded signature algorithm parameters from this certificate's signature algorithm.
`abstract byte[]` | `getSignature()` Gets the `signature` value (the raw signature bits) from the certificate.
`abstract Principal` | `getSubjectDN()` Gets the `subject` (subject distinguished name) value from the certificate.
`abstract boolean[]` | `getSubjectUniqueID()` Gets the `subjectUniqueID` value from the certificate.
`abstract byte[]` | `getTBSCertificate()` Gets the DER-encoded certificate information, the `tbsCertificate` from this certificate.
`abstract int` | `getVersion()` Gets the `version` (version number) value from the certificate.

Methods inherited from class java.security.cert.Certificate
`equals, getEncoded, getPublicKey, getType, hashCode, toString, verify, verify, writeReplace`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Methods inherited from interface java.security.cert.X509Extension
`getCriticalExtensionOIDs, getExtensionValue, getNonCriticalExtensionOIDs, hasUnsupportedCriticalExtension`

Constructor Detail

### X509Certificate

    protected X509Certificate()

  Constructor for X.509 certificates.

Method Detail

### checkValidity

    public abstract void checkValidity()
                                throws CertificateExpiredException,
                                       CertificateNotYetValidException

  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:
    `CertificateExpiredException` - if the certificate has expired.
    `CertificateNotYetValidException` - if the certificate is not yet valid.

### checkValidity

    public abstract void checkValidity(Date date)
                                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.
  Parameters:
    `date` - the Date to check against to see if this certificate is valid at that date/time.
  Throws:
    `CertificateExpiredException` - if the certificate has expired with respect to the `date` supplied.
    `CertificateNotYetValidException` - if the certificate is not yet valid with respect to the `date` supplied.
  See Also:
    `checkValidity()`

### getVersion

    public abstract int getVersion()

  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.

### getSerialNumber

    public abstract BigInteger getSerialNumber()

  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.

### getIssuerDN

    public abstract Principal getIssuerDN()

  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.

### getSubjectDN

    public abstract Principal getSubjectDN()

  Gets the `subject` (subject distinguished name) value from the certificate. 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.

### getNotBefore

    public abstract Date getNotBefore()

  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 }

  Returns:
    the start date of the validity period.
  See Also:
    `checkValidity()`

### getNotAfter

    public abstract Date getNotAfter()

  Gets the `notAfter` date from the validity period of the certificate. See `getNotBefore` for relevant ASN.1 definitions.
  Returns:
    the end date of the validity period.
  See Also:
    `checkValidity()`

### getTBSCertificate

    public abstract byte[] getTBSCertificate()
                                      throws CertificateEncodingException

  Gets the DER-encoded certificate information, the `tbsCertificate` from this certificate. This can be used to verify the signature independently.
  Returns:
    the DER-encoded certificate information.
  Throws:
    `CertificateEncodingException` - if an encoding error occurs.

### getSignature

    public abstract byte[] getSignature()

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

       signature     BIT STRING

  Returns:
    the signature.

### getSigAlgName

    public abstract String getSigAlgName()

  Gets the signature algorithm name for the certificate signature algorithm. An example is the string "SHA-1/DSA". 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.

### getSigAlgOID

    public abstract String getSigAlgOID()

  Gets the signature algorithm OID string from the certificate. An OID is represented by a set of positive whole numbers separated by periods. For example, the string "1.2.840.10040.4.3" identifies the SHA-1 with DSA signature algorithm, as per RFC 2459.

  See `getSigAlgName` for relevant ASN.1 definitions.

  Returns:
    the signature algorithm OID string.

### getSigAlgParams

    public abstract byte[] getSigAlgParams()

  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.

### getIssuerUniqueID

    public abstract boolean[] getIssuerUniqueID()

  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 2459 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.

### getSubjectUniqueID

    public abstract boolean[] getSubjectUniqueID()

  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.

### getKeyUsage

    public abstract boolean[] getKeyUsage()

  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 2459 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.

### getBasicConstraints

    public abstract int getBasicConstraints()

  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.

  Note that for RFC 2459 this extension is always marked critical if `cA` is TRUE, meaning this certificate belongs to a Certificate Authority.

  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.

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