SignatureSpi

public abstract class SignatureSpi extends Object

Known Direct Subclasses Signature Signature The Signature class is used to provide applications the functionality of a digital signature algorithm.

This class defines the Service Provider Interface (SPI) for the Signature class, which is used to provide the functionality of a digital signature algorithm. Digital signatures are used for authentication and integrity assurance of digital data. .

All the abstract methods in this class must be implemented by each cryptographic service provider who wishes to supply the implementation of a particular signature algorithm.

See Also

• Signature

Field Summary

protected SecureRandom

appRandom

Application-specified source of randomness.

Public Constructor Summary

SignatureSpi()

Public Method Summary

Object

clone() Returns a clone if the implementation is cloneable.

Protected Method Summary

abstract Object	engineGetParameter(String param) This method is deprecated. Deprecated.
AlgorithmParameters	engineGetParameters() This method is overridden by providers to return the parameters used with this signature engine, or null if this signature engine does not use any parameters.
void	engineInitSign(PrivateKey privateKey, SecureRandom random) Initializes this signature object with the specified private key and source of randomness for signing operations.
abstract void	engineInitSign(PrivateKey privateKey) Initializes this signature object with the specified private key for signing operations.
abstract void	engineInitVerify(PublicKey publicKey) Initializes this signature object with the specified public key for verification operations.
abstract void	engineSetParameter(String param, Object value) This method is deprecated. Replaced by engineSetParameter.
void	engineSetParameter(AlgorithmParameterSpec params) This method is overridden by providers to initialize this signature engine with the specified parameter set.
abstract byte[]	engineSign() Returns the signature bytes of all the data updated so far.
int	engineSign(byte[] outbuf, int offset, int len) Finishes this signature operation and stores the resulting signature bytes in the provided buffer outbuf, starting at offset.
abstract void	engineUpdate(byte[] b, int off, int len) Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset.
void	engineUpdate(ByteBuffer input) Updates the data to be signed or verified using the specified ByteBuffer.
abstract void	engineUpdate(byte b) Updates the data to be signed or verified using the specified byte.
boolean	engineVerify(byte[] sigBytes, int offset, int length) Verifies the passed-in signature in the specified array of bytes, starting at the specified offset.
abstract boolean	engineVerify(byte[] sigBytes) Verifies the passed-in signature.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Fields

protected SecureRandom appRandom

Application-specified source of randomness.

Public Constructors

public SignatureSpi ()

Public Methods

public Object clone ()

Returns a clone if the implementation is cloneable.

Returns

• a clone if the implementation is cloneable.

Throws

CloneNotSupportedException	if this is called on an implementation that does not support Cloneable.

Protected Methods

protected abstract Object engineGetParameter (String param)

This method is deprecated.
Deprecated.

Gets the value of the specified algorithm parameter. This method supplies a general-purpose mechanism through which it is possible to get the various parameters of this object. A parameter may be any settable parameter for the algorithm, such as a parameter size, or a source of random bits for signature generation (if appropriate), or an indication of whether or not to perform a specific but optional computation. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

Parameters

param	the string name of the parameter.

Returns

• the object that represents the parameter value, or null if there is none.

Throws

InvalidParameterException	if param is an invalid parameter for this engine, or another exception occurs while trying to get this parameter.

protected AlgorithmParameters engineGetParameters ()

This method is overridden by providers to return the parameters used with this signature engine, or null if this signature engine does not use any parameters.

The returned parameters may be the same that were used to initialize this signature engine, or may contain a combination of default and randomly generated parameter values used by the underlying signature implementation if this signature engine requires algorithm parameters but was not initialized with any.

Returns

• the parameters used with this signature engine, or null if this signature engine does not use any parameters

Throws

UnsupportedOperationException	if this method is not overridden by a provider

protected void engineInitSign (PrivateKey privateKey, SecureRandom random)

Initializes this signature object with the specified private key and source of randomness for signing operations.

This concrete method has been added to this previously-defined abstract class. (For backwards compatibility, it cannot be abstract.)

Parameters

privateKey	the private key of the identity whose signature will be generated.
random	the source of randomness

Throws

InvalidKeyException	if the key is improperly encoded, parameters are missing, and so on.

protected abstract void engineInitSign (PrivateKey privateKey)

Initializes this signature object with the specified private key for signing operations.

Parameters

privateKey	the private key of the identity whose signature will be generated.

Throws

InvalidKeyException	if the key is improperly encoded, parameters are missing, and so on.

protected abstract void engineInitVerify (PublicKey publicKey)

Initializes this signature object with the specified public key for verification operations.

Parameters

publicKey	the public key of the identity whose signature is going to be verified.

Throws

InvalidKeyException	if the key is improperly encoded, parameters are missing, and so on.

protected abstract void engineSetParameter (String param, Object value)

This method is deprecated.
Replaced by engineSetParameter.

Sets the specified algorithm parameter to the specified value. This method supplies a general-purpose mechanism through which it is possible to set the various parameters of this object. A parameter may be any settable parameter for the algorithm, such as a parameter size, or a source of random bits for signature generation (if appropriate), or an indication of whether or not to perform a specific but optional computation. A uniform algorithm-specific naming scheme for each parameter is desirable but left unspecified at this time.

Parameters

param	the string identifier of the parameter.
value	the parameter value.

Throws

InvalidParameterException	if param is an invalid parameter for this signature algorithm engine, the parameter is already set and cannot be set again, a security exception occurs, and so on.

protected void engineSetParameter (AlgorithmParameterSpec params)

This method is overridden by providers to initialize this signature engine with the specified parameter set.

Parameters

params	the parameters

Throws

UnsupportedOperationException	if this method is not overridden by a provider
InvalidAlgorithmParameterException	if this method is overridden by a provider and the given parameters are inappropriate for this signature engine

protected abstract byte[] engineSign ()

Returns the signature bytes of all the data updated so far. The format of the signature depends on the underlying signature scheme.

Returns

• the signature bytes of the signing operation's result.

Throws

SignatureException	if the engine is not initialized properly or if this signature algorithm is unable to process the input data provided.

protected int engineSign (byte[] outbuf, int offset, int len)

Finishes this signature operation and stores the resulting signature bytes in the provided buffer outbuf, starting at offset. The format of the signature depends on the underlying signature scheme.

The signature implementation is reset to its initial state (the state it was in after a call to one of the engineInitSign methods) and can be reused to generate further signatures with the same private key. This method should be abstract, but we leave it concrete for binary compatibility. Knowledgeable providers should override this method.

Parameters

outbuf	buffer for the signature result.
offset	offset into outbuf where the signature is stored.
len	number of bytes within outbuf allotted for the signature. Both this default implementation and the SUN provider do not return partial digests. If the value of this parameter is less than the actual signature length, this method will throw a SignatureException. This parameter is ignored if its value is greater than or equal to the actual signature length.

Returns

• the number of bytes placed into outbuf

Throws

SignatureException	if the engine is not initialized properly, if this signature algorithm is unable to process the input data provided, or if len is less than the actual signature length.

protected abstract void engineUpdate (byte[] b, int off, int len)

Updates the data to be signed or verified, using the specified array of bytes, starting at the specified offset.

Parameters

b	the array of bytes
off	the offset to start from in the array of bytes
len	the number of bytes to use, starting at offset

Throws

SignatureException	if the engine is not initialized properly

protected void engineUpdate (ByteBuffer input)

Updates the data to be signed or verified using the specified ByteBuffer. Processes the data.remaining() bytes starting at at data.position(). Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

Parameters

input	the ByteBuffer

protected abstract void engineUpdate (byte b)

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

Parameters

b	the byte to use for the update.

Throws

SignatureException	if the engine is not initialized properly.

protected boolean engineVerify (byte[] sigBytes, int offset, int length)

Verifies the passed-in signature in the specified array of bytes, starting at the specified offset.

Note: Subclasses should overwrite the default implementation.

Parameters

sigBytes	the signature bytes to be verified.
offset	the offset to start from in the array of bytes.
length	the number of bytes to use, starting at offset.

Returns

• true if the signature was verified, false if not.

Throws

SignatureException	if the engine is not initialized properly, the passed-in signature is improperly encoded or of the wrong type, if this signature algorithm is unable to process the input data provided, etc.

protected abstract boolean engineVerify (byte[] sigBytes)

Verifies the passed-in signature.

Parameters

sigBytes	the signature bytes to be verified.

Returns

• true if the signature was verified, false if not.

Throws

SignatureException	if the engine is not initialized properly, the passed-in signature is improperly encoded or of the wrong type, if this signature algorithm is unable to process the input data provided, etc.