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Class javax.security.cert.X509Certificate 

java.lang.Object
   |
   +----javax.security.cert.Certificate
           |
           +----javax.security.cert.X509Certificate
public abstract class X509Certificate
extends Certificate

Abstract class for X.509 v1 certificates. This provides a standard way to access all the version 1 attributes of an X.509 certificate. Attributes that are specific to X.509 v2 or v3 are not available through this interface. Future API evolution will provide full access to complete X.509 v3 attributes.

The basic X.509 format was defined by ISO/IEC and ANSI X9 and 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.

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,
     }

Here is sample code to instantiate an X.509 certificate: 

 
 InputStream inStream = new FileInputStream("fileName-of-cert");
 X509Certificate cert = X509Certificate.getInstance(inStream);
 inStream.close();
OR 
 byte[] certData = <certificate read from a file, say>
 X509Certificate cert = X509Certificate.getInstance(certData);

In either case, the code that instantiates an X.509 certificate consults the Java security properties file to locate the actual implementation or instantiates a default implementation.

The Java security properties file is located in the file named <JAVA_HOME>/lib/security/java.security, where <JAVA_HOME> refers to the directory where the JDK was installed. In the Security properties file, a default implementation for X.509 v1 may be given such as: 

 cert.provider.x509v1=sun.security.x509.X509V1CertImpl

The value of this cert.provider.x509v1 property has to be changed to instatiate another implementation. If this security property is not set, a default implementation will be used.

See Also:
Certificate, X509Extension

Constructor Index

o X509Certificate()

Method Index

o checkValidity()
Checks that the certificate is currently valid.
o checkValidity(Date)
Checks that the specified date is within the certificate's validity period.
o getInstance(byte[])
Instantiates an X509Certificate object, and initializes it with the specified byte array.
o getInstance(InputStream)
Instantiates an X509Certificate object, and initializes it with the data read from the input stream inStream.
o getIssuerDN()
Gets the issuer (issuer distinguished name) value from the certificate.
o getNotAfter()
Gets the notAfter date from the validity period of the certificate.
o getNotBefore()
Gets the notBefore date from the validity period of the certificate.
o getSerialNumber()
Gets the serialNumber value from the certificate.
o getSigAlgName()
Gets the signature algorithm name for the certificate signature algorithm.
o getSigAlgOID()
Gets the signature algorithm OID string from the certificate.
o getSigAlgParams()
Gets the DER-encoded signature algorithm parameters from this certificate's signature algorithm.
o getSubjectDN()
Gets the subject (subject distinguished name) value from the certificate.
o getVersion()
Gets the version (version number) value from the certificate.

Constructors

o X509Certificate 
 public X509Certificate()

Methods

o getInstance 
 public static final X509Certificate getInstance(InputStream inStream) throws CertificateException
Instantiates an X509Certificate object, and initializes it with the data read from the input stream inStream. The implementation (X509Certificate is an abstract class) is provided by the class specified as the value of the cert.provider.x509v1 property in the security properties file.

Note: Only one DER-encoded certificate is expected to be in the input stream. Also, all X509Certificate subclasses must provide a constructor of the form: 

 public <subClass>(InputStream inStream) ...

Parameters:
inStream - an input stream with the data to be read to initialize the certificate.
Returns:
an X509Certificate object initialized with the data from the input stream.
Throws: CertificateException
if a class initialization or certificate parsing error occurs.
o getInstance 
 public static final X509Certificate getInstance(byte certData[]) throws CertificateException
Instantiates an X509Certificate object, and initializes it with the specified byte array. The implementation (X509Certificate is an abstract class) is provided by the class specified as the value of the cert.provider.x509v1 property in the security properties file.

Note: All X509Certificate subclasses must provide a constructor of the form: 

 public <subClass>(InputStream inStream) ...

Parameters:
certData - a byte array containing the DER-encoded certificate.
Returns:
an X509Certificate object initialized with the data from certData.
Throws: CertificateException
if a class initialization or certificate parsing error occurs.
o 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.
Throws: CertificateNotYetValidException
if the certificate is not yet valid.
o checkValidity 
 public abstract void checkValidity(Date date) throws CertificateExpiredException, CertificateNotYetValidException
Checks that the specified date is within the certificate's validity period. In other words, this determines whether the certificate would be valid at the specified 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.
Throws: CertificateNotYetValidException
if the certificate is not yet valid with respect to the date supplied.
See Also:
checkValidity
o 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.
o 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.
o 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.
o 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.
o 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
o 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
o 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.
o 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 the PKIX part I.

See getSigAlgName for relevant ASN.1 definitions.

Returns:
the signature algorithm OID string.
o 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.

See getSigAlgName for relevant ASN.1 definitions.

Returns:
the DER-encoded signature algorithm parameters, or null if no parameters are present. 
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