SignatureSpi

public abstract class SignatureSpi extends Object
Known Direct Subclasses

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

Field Summary

protected SecureRandom appRandom Application-specified source of randomness.

Public Constructor Summary

Public Method Summary

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

Protected Method Summary

abstract Object
engineGetParameter(String param)
This method was 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 was 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

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 was 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 was 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.