http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.crypto;

import java.math.BigInteger;


interface for classes implementing algorithms modeled similar to the Digital Signature Alorithm.

/**
 * interface for classes implementing algorithms modeled similar to the Digital Signature Alorithm.
 */
public interface DSA
{
    
initialise the signer for signature generation or signature
verification.

Params:
  • forSigning – true if we are generating a signature, false
otherwise.
  • param – key parameters for signature generation.
/**
     * initialise the signer for signature generation or signature
     * verification.
     *
     * @param forSigning true if we are generating a signature, false
     * otherwise.
     * @param param key parameters for signature generation.
     */
    public void init(boolean forSigning, CipherParameters param);

    
sign the passed in message (usually the output of a hash function).

Params:
  • message – the message to be signed.
Returns:two big integers representing the r and s values respectively.
/**
     * sign the passed in message (usually the output of a hash function).
     *
     * @param message the message to be signed.
     * @return two big integers representing the r and s values respectively.
     */
    public BigInteger[] generateSignature(byte[] message);

    
verify the message message against the signature values r and s.

Params:
  • message – the message that was supposed to have been signed.
  • r – the r signature value.
  • s – the s signature value.
/**
     * verify the message message against the signature values r and s.
     *
     * @param message the message that was supposed to have been signed.
     * @param r the r signature value.
     * @param s the s signature value.
     */
    public boolean verifySignature(byte[] message, BigInteger  r, BigInteger s);
}