org.spongycastle.crypto.signers

Class DSASigner

java.lang.Object

org.spongycastle.crypto.signers.DSASigner

All Implemented Interfaces:

DSA

public class DSASigner
extends java.lang.Object
implements DSA

The Digital Signature Algorithm - as described in "Handbook of Applied Cryptography", pages 452 - 453.

Constructor Summary

Constructors

Constructor and Description
DSASigner() Default configuration, random K values.
DSASigner(DSAKCalculator kCalculator) Configuration with an alternate, possibly deterministic calculator of K.

Method Summary

Modifier and Type	Method and Description
java.math.BigInteger[]	generateSignature(byte[] message) generate a signature for the given message using the key we were initialised with.
void	init(boolean forSigning, CipherParameters param) initialise the signer for signature generation or signature verification.
protected java.security.SecureRandom	initSecureRandom(boolean needed, java.security.SecureRandom provided)
boolean	verifySignature(byte[] message, java.math.BigInteger r, java.math.BigInteger s) return true if the value r and s represent a DSA signature for the passed in message for standard DSA the message should be a SHA-1 hash of the real message to be verified.

Methods inherited from class java.lang.Object

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

Constructor Detail

DSASigner

public DSASigner()

Default configuration, random K values.

DSASigner

public DSASigner(DSAKCalculator kCalculator)

Configuration with an alternate, possibly deterministic calculator of K.

Parameters:

kCalculator - a K value calculator.

Method Detail

init

public void init(boolean forSigning,
                 CipherParameters param)

Description copied from interface: DSA

initialise the signer for signature generation or signature verification.

Specified by:

init in interface DSA

Parameters:

forSigning - true if we are generating a signature, false otherwise.

param - key parameters for signature generation.

generateSignature

public java.math.BigInteger[] generateSignature(byte[] message)

generate a signature for the given message using the key we were initialised with. For conventional DSA the message should be a SHA-1 hash of the message of interest.

Specified by:

generateSignature in interface DSA

Parameters:

message - the message that will be verified later.

Returns:

two big integers representing the r and s values respectively.

verifySignature

public boolean verifySignature(byte[] message,
                               java.math.BigInteger r,
                               java.math.BigInteger s)

return true if the value r and s represent a DSA signature for the passed in message for standard DSA the message should be a SHA-1 hash of the real message to be verified.

Specified by:

verifySignature in interface DSA

Parameters:

message - the message that was supposed to have been signed.

r - the r signature value.

s - the s signature value.

initSecureRandom

protected java.security.SecureRandom initSecureRandom(boolean needed,
                                                      java.security.SecureRandom provided)