java.security

Class Signature

java.lang.Object

java.security.SignatureSpi

java.security.Signature

public abstract class Signature
extends SignatureSpi

Signature is used to provide an interface to digital signature algorithms. Digital signatures provide authentication and data integrity of digital data.

The GNU provider provides the NIST standard DSA which uses DSA and SHA-1. It can be specified by SHA/DSA, SHA-1/DSA or its OID. If the RSA signature algorithm is provided then it could be MD2/RSA. MD5/RSA, or SHA-1/RSA. The algorithm must be specified because there is no default.

Signature provides implementation-independent algorithms which are requested by the user through the getInstance() methods. It can be requested by specifying just the algorithm name or by specifying both the algorithm name and provider name.

The three phases of using Signature are:

1. Initializing:
   • It must be initialized with a private key for signing.
   • It must be initialized with a public key for verifying.
   • Updating:

     Update the bytes for signing or verifying with calls to update.

   • Signing or Verify the signature on the currently stored bytes by calling sign or verify.

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	SIGN Possible state value which signifies that this instance has been initialized for signing purposes.
protected int	state Current sate of this instance.
protected static int	UNINITIALIZED Possible state value which signifies that this instance has not yet been initialized.
protected static int	VERIFY Possible state value which signifies that this instance has been initialized for verification purposes.

Fields inherited from class java.security.SignatureSpi

appRandom

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Signature(java.lang.String algorithm) Constructs a new Signature instance for a designated digital signature algorithm.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Object	clone() Returns a clone of this instance.
java.lang.String	getAlgorithm() Returns the name of the algorithm currently used.
static Signature	getInstance(java.lang.String algorithm) Returns an instance of Signature representing the specified signature.
static Signature	getInstance(java.lang.String algorithm, Provider provider) Returns an instance of Signature representing the specified signature from the specified Provider.
static Signature	getInstance(java.lang.String algorithm, java.lang.String provider) Returns an instance of Signature representing the specified signature from the named provider.
java.lang.Object	getParameter(java.lang.String param) Deprecated. use the other getParameter
AlgorithmParameters	getParameters() Return the parameters of the algorithm used in this instance as an AlgorithmParameters.
Provider	getProvider() Returns the Provider of this instance.
void	initSign(PrivateKey privateKey) Initializes this class with the private key for signing purposes.
void	initSign(PrivateKey privateKey, SecureRandom random) Initializes this class with the private key and source of randomness for signing purposes.
void	initVerify(java.security.cert.Certificate certificate) Verify a signature with a designated Certificate.
void	initVerify(PublicKey publicKey) Initializes this instance with the public key for verification purposes.
void	setParameter(java.security.spec.AlgorithmParameterSpec params) Sets the signature engine with the specified AlgorithmParameterSpec.
void	setParameter(java.lang.String param, java.lang.Object value) Deprecated. use the other setParameter
byte[]	sign() Returns the signature bytes of all the data fed to this instance.
int	sign(byte[] outbuf, int offset, int len) Generates signature bytes of all the data fed to this instance and stores it in the designated array.
java.lang.String	toString() Returns a rstring representation of this instance.
void	update(byte b) Updates the data to be signed or verified with the specified byte.
void	update(byte[] data) Updates the data to be signed or verified with the specified bytes.
void	update(byte[] data, int off, int len) Updates the data to be signed or verified with the specified bytes.
void	update(java.nio.ByteBuffer input) Update this signature with the Buffer.remaining() bytes of the input buffer.
boolean	verify(byte[] signature) Verifies a designated signature.
boolean	verify(byte[] signature, int offset, int length) Verifies a designated signature.

Methods inherited from class java.security.SignatureSpi

engineGetParameter, engineGetParameters, engineInitSign, engineInitSign, engineInitVerify, engineSetParameter, engineSetParameter, engineSign, engineSign, engineUpdate, engineUpdate, engineUpdate, engineVerify, engineVerify

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

UNINITIALIZED

protected static final int UNINITIALIZED

Possible state value which signifies that this instance has not yet been initialized.

See Also:

Constant Field Values

SIGN

protected static final int SIGN

Possible state value which signifies that this instance has been initialized for signing purposes.

See Also:

Constant Field Values

VERIFY

protected static final int VERIFY

Possible state value which signifies that this instance has been initialized for verification purposes.

See Also:

Constant Field Values

state

protected int state

Current sate of this instance.

Constructor Detail

Signature

protected Signature(java.lang.String algorithm)

Constructs a new Signature instance for a designated digital signature algorithm.

Parameters:

algorithm - the algorithm to use.

Method Detail

getInstance

public static Signature getInstance(java.lang.String algorithm)
                             throws NoSuchAlgorithmException

Returns an instance of Signature representing the specified signature.

Parameters:

algorithm - the algorithm to use.

Returns:

a new instance repesenting the desired algorithm.

Throws:

NoSuchAlgorithmException - if the algorithm is not implemented by any provider.

java.lang.IllegalArgumentException - if algorithm is null or is an empty string.

getInstance

public static Signature getInstance(java.lang.String algorithm,
                    java.lang.String provider)
                             throws NoSuchAlgorithmException,
                                    NoSuchProviderException

Returns an instance of Signature representing the specified signature from the named provider.

Parameters:

algorithm - the algorithm to use.

provider - the name of the provider to use.

Returns:

a new instance repesenting the desired algorithm.

Throws:

NoSuchProviderException - if the named provider was not found.

NoSuchAlgorithmException - if the algorithm is not implemented by the named provider.

java.lang.IllegalArgumentException - if either algorithm or provider is null or empty.

getInstance

public static Signature getInstance(java.lang.String algorithm,
                    Provider provider)
                             throws NoSuchAlgorithmException

Returns an instance of Signature representing the specified signature from the specified Provider.

Parameters:

algorithm - the algorithm to use.

provider - the Provider to use.

Returns:

a new instance repesenting the desired algorithm.

Throws:

NoSuchAlgorithmException - if the algorithm is not implemented by the Provider.

java.lang.IllegalArgumentException - if either algorithm or provider is null, or if algorithm is an empty string.

getProvider

public final Provider getProvider()

Returns the Provider of this instance.

Returns:

the Provider of this instance.

initVerify

public final void initVerify(PublicKey publicKey)
                      throws InvalidKeyException

Initializes this instance with the public key for verification purposes.

Parameters:

publicKey - the public key to verify with.

Throws:

InvalidKeyException - if the key is invalid.

initVerify

public final void initVerify(java.security.cert.Certificate certificate)
                      throws InvalidKeyException

Verify a signature with a designated Certificate. This is a FIPS 140-1 compatible method since it verifies a signature with a certificate.

If the Certificate is an X.509 one, has a KeyUsage parameter and that parameter indicates this key is not to be used for signing then an exception is thrown.

Parameters:

certificate - a Certificate containing a public key to verify with.

Throws:

InvalidKeyException - if the key is invalid.

initSign

public final void initSign(PrivateKey privateKey)
                    throws InvalidKeyException

Initializes this class with the private key for signing purposes.

Parameters:

privateKey - the private key to sign with.

Throws:

InvalidKeyException - if the key is invalid.

initSign

public final void initSign(PrivateKey privateKey,
            SecureRandom random)
                    throws InvalidKeyException

Initializes this class with the private key and source of randomness for signing purposes.

Parameters:

privateKey - the private key to sign with.

random - the SecureRandom to use.

Throws:

InvalidKeyException - if the key is invalid.

sign

public final byte[] sign()
                  throws SignatureException

Returns the signature bytes of all the data fed to this instance. The format of the output depends on the underlying signature algorithm.

Returns:

the signature bytes.

Throws:

SignatureException - if the engine is not properly initialized.

sign

public final int sign(byte[] outbuf,
       int offset,
       int len)
               throws SignatureException

Generates signature bytes of all the data fed to this instance and stores it in the designated array. The format of the result depends on the underlying signature algorithm.

After calling this method, the instance is reset to its initial state and can then be used to generate additional signatures.

IMPLEMENTATION NOTE: Neither this method nor the GNU provider will return partial digests. If len is less than the signature length, this method will throw a SignatureException. If it is greater than or equal then it is ignored.

Parameters:

outbuf - array of bytes of where to store the resulting signature bytes.

offset - the offset to start at in the array.

len - the number of the bytes to use in the array.

Returns:

the real number of bytes used.

Throws:

SignatureException - if the engine is not properly initialized.

Since:

1.2

verify

public final boolean verify(byte[] signature)
                     throws SignatureException

Verifies a designated signature.

Parameters:

signature - the signature bytes to verify.

Returns:

true if verified, false otherwise.

Throws:

SignatureException - if the engine is not properly initialized or the signature does not check.

verify

public final boolean verify(byte[] signature,
             int offset,
             int length)
                     throws SignatureException

Verifies a designated signature.

Parameters:

signature - the signature bytes to verify.

offset - the offset to start at in the array.

length - the number of the bytes to use from the array.

Returns:

true if verified, false otherwise.

Throws:

java.lang.IllegalArgumentException - if the signature byte array is null, or the offset or length is less than 0, or the sum of the offset and length is greater than the length of the signature byte array.

SignatureException - if the engine is not properly initialized or the signature does not check.

update

public final void update(byte b)
                  throws SignatureException

Updates the data to be signed or verified with the specified byte.

Parameters:

b - the byte to update with.

Throws:

SignatureException - if the engine is not properly initialized.

update

public final void update(byte[] data)
                  throws SignatureException

Updates the data to be signed or verified with the specified bytes.

Parameters:

data - the array of bytes to use.

Throws:

SignatureException - if the engine is not properly initialized.

update

public final void update(byte[] data,
          int off,
          int len)
                  throws SignatureException

Updates the data to be signed or verified with the specified bytes.

Parameters:

data - an array of bytes to use.

off - the offset to start at in the array.

len - the number of bytes to use from the array.

Throws:

SignatureException - if the engine is not properly initialized.

update

public final void update(java.nio.ByteBuffer input)
                  throws SignatureException

Update this signature with the Buffer.remaining() bytes of the input buffer.

Parameters:

input - The input buffer.

Throws:

SignatureException - If this instance was not properly initialized.

getAlgorithm

public final java.lang.String getAlgorithm()

Returns the name of the algorithm currently used. The names of algorithms are usually SHA/DSA or SHA/RSA.

Returns:

name of algorithm.

toString

public java.lang.String toString()

Returns a rstring representation of this instance.

Overrides:

toString in class java.lang.Object

Returns:

a rstring representation of this instance.

See Also:

Object.getClass(), Object.hashCode(), Class.getName(), Integer.toHexString(int)

setParameter

public final void setParameter(java.lang.String param,
                java.lang.Object value)
                        throws InvalidParameterException

Deprecated. use the other setParameter

Sets the specified algorithm parameter to the specified value.

Parameters:

param - the parameter name.

value - the parameter value.

Throws:

InvalidParameterException - if the parameter is invalid, the parameter is already set and can not be changed, a security exception occured, etc.

setParameter

public final void setParameter(java.security.spec.AlgorithmParameterSpec params)
                        throws InvalidAlgorithmParameterException

Sets the signature engine with the specified AlgorithmParameterSpec.

By default, and unless overriden by the concrete SPI, this method always throws an UnsupportedOperationException.

Parameters:

params - the parameters to use for intializing this instance.

Throws:

InvalidParameterException - if the parameter is invalid, the parameter is already set and cannot be changed, a security exception occured, etc.

InvalidAlgorithmParameterException

getParameters

public final AlgorithmParameters getParameters()

Return the parameters of the algorithm used in this instance as an AlgorithmParameters.

Returns:

the parameters used with this instance, or null if this instance does not use any parameters.

getParameter

public final java.lang.Object getParameter(java.lang.String param)
                                    throws InvalidParameterException

Deprecated. use the other getParameter

Returns the value for the specified algorithm parameter.

Parameters:

param - the parameter name.

Returns:

the parameter value.

Throws:

InvalidParameterException - if the parameter is invalid.

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Returns a clone of this instance.

Overrides:

clone in class SignatureSpi

Returns:

a clone of this instace.

Throws:

java.lang.CloneNotSupportedException - if the implementation does not support cloning.

See Also:

Cloneable