java.security

Class SignatureSpi

java.lang.Object

java.security.SignatureSpi

Direct Known Subclasses:

Signature

public abstract class SignatureSpi
extends Object

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.

Author:

Benjamin Renaud

See Also:

Signature

Field Summary

Fields

Modifier and Type	Field and Description
protected SecureRandom	appRandom Application-specified source of randomness.

Constructor Summary

Constructors

Constructor and Description
SignatureSpi()

Method Summary

Modifier and Type	Method and Description
Object	clone() Returns a clone if the implementation is cloneable.
protected abstract void	engineInitSign(PrivateKey privateKey) Initializes this signature object with the specified private key for signing operations.
protected void	engineInitSign(PrivateKey privateKey, SecureRandom random) Initializes this signature object with the specified private key and source of randomness for signing operations.
protected abstract void	engineInitVerify(PublicKey publicKey) Initializes this signature object with the specified public key for verification operations.
protected void	engineSetParameter(AlgorithmParameterSpec params) This method is overridden by providers to initialize this signature engine with the specified parameter set.
protected abstract byte[]	engineSign() Returns the signature bytes of all the data updated so far.
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.
protected abstract void	engineUpdate(byte b) Updates the data to be signed or verified using the specified byte.
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.
protected abstract boolean	engineVerify(byte[] sigBytes) Verifies the passed-in signature.
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.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

appRandom

@Nullable
protected SecureRandom appRandom

Application-specified source of randomness.

Constructor Detail

SignatureSpi

public SignatureSpi()

Method Detail

clone

public Object clone()
             throws CloneNotSupportedException

Returns a clone if the implementation is cloneable.

Overrides:

clone in class Object

Returns:

a clone if the implementation is cloneable.

Throws:

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

See Also:

Cloneable

engineInitSign

protected abstract void engineInitSign(PrivateKey privateKey)
                                throws InvalidKeyException

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.

engineInitSign

protected void engineInitSign(PrivateKey privateKey,
                              SecureRandom random)
                       throws InvalidKeyException

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.

engineInitVerify

protected abstract void engineInitVerify(PublicKey publicKey)
                                  throws InvalidKeyException

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.

engineSetParameter

protected void engineSetParameter(AlgorithmParameterSpec params)
                           throws InvalidAlgorithmParameterException

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

engineSign

protected abstract byte[] engineSign()
                              throws SignatureException

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.

engineSign

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

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.

Since:

1.2

engineUpdate

protected abstract void engineUpdate(byte b)
                              throws SignatureException

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.

engineUpdate

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

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

engineVerify

protected abstract boolean engineVerify(byte[] sigBytes)
                                 throws SignatureException

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.

engineVerify

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

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.

Since:

1.4