This class defines the Service Provider Interface (SPI) for the * {@link 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.
*
* @author Mark Benvenuto 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.) Finishes this signature operation and stores the resulting signature
* bytes in the provided buffer The signature implementation is reset to its initial state (the state it
* was in after a call to one of the Verifies the passed-in Note: Subclasses should overwrite the default implementation. This method is overridden by providers to return the parameters used
* with this signature engine, or 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.outbuf, starting at offset
* . The format of the signature depends on the underlying signature
* scheme.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.outbuf.
* @throws SignatureException if an error occurs or len is less than the
* actual signature length.
* @since 1.2
*/
protected int engineSign(byte[] outbuf, int offset, int len)
throws SignatureException
{
byte tmp[] = engineSign();
if (tmp.length > len)
throw new SignatureException("Invalid Length");
System.arraycopy(outbuf, offset, tmp, 0, tmp.length);
return tmp.length;
}
/**
* Verifies the passed-in signature.
*
* @param sigBytes the signature bytes to be verified.
* @return true if the signature was verified, false
* if not.
* @throws SignatureException if the engine is not initialized properly, or
* the passed-in signature is improperly encoded or of the wrong type, etc.
*/
protected abstract boolean engineVerify(byte[] sigBytes)
throws SignatureException;
/**
* signature in the specified array of
* bytes, starting at the specified offset.true if the signature was verified, false
* if not.
* @throws SignatureException if the engine is not initialized properly, or
* the passed-in signature is improperly encoded or of the wrong
* type, etc.
*/
protected boolean engineVerify(byte[] sigBytes, int offset, int length)
throws SignatureException
{
byte[] tmp = new byte[length];
System.arraycopy(sigBytes, offset, tmp, 0, length);
return engineVerify(tmp);
}
/**
* 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.
*
* @param param the string identifier of the parameter.
* @param 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.
* @deprecated Replaced by engineSetParameter(AlgorithmParameterSpec).
*/
protected abstract void engineSetParameter(String param, Object value)
throws InvalidParameterException;
/**
* This method is overridden by providers to initialize this signature engine
* with the specified parameter set.
*
* @param params the parameters.
* @throws UnsupportedOperationException if this method is not overridden by
* a provider.
* @throws InvalidAlgorithmParameterException if this method is overridden by
* a provider and the the given parameters are inappropriate for this
* signature engine.
*/
protected void engineSetParameter(AlgorithmParameterSpec params)
throws InvalidAlgorithmParameterException
{
throw new UnsupportedOperationException();
}
/**
* null if this signature engine
* does not use any parameters.null
* if this signature engine does not use any parameters.
* @throws UnsupportedOperationException if this method is not overridden by
* a provider.
*/
protected AlgorithmParameters engineGetParameters()
{
throw new UnsupportedOperationException();
}
/**
* 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.
*
* @param param the string name of the parameter.
* @return 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.
* @deprecated
*/
protected abstract Object engineGetParameter(String param)
throws InvalidParameterException;
/**
* Returns a clone if the implementation is cloneable.
*
* @return a clone if the implementation is cloneable.
* @throws CloneNotSupportedException if this is called on an implementation
* that does not support {@link Cloneable}.
* @see Cloneable
*/
public Object clone() throws CloneNotSupportedException
{
throw new CloneNotSupportedException();
}
}