any_elgamal_pkcs1signature.java

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// $Id: Any_ElGamal_PKCS1Signature.java,v 1.1.1.1 2002/08/27 12:32:10 grosbois Exp $
//
// $Log: Any_ElGamal_PKCS1Signature.java,v $
// Revision 1.1.1.1  2002/08/27 12:32:10  grosbois
// Add cryptix 3.2
//
// Revision 1.4  2000/08/17 11:40:54  edwin
// java.* -> xjava.*
//
// Revision 1.3  1997/12/14 17:37:58  hopwood
// + Committed changes below.
//
// Revision 1.2.1  1997/12/10  hopwood
// + initInternal was checking p before it was set.
// + Cosmetics.
//
// Revision 1.2  1997/12/10 01:17:46  raif
// + documentation.
// + use cryptix.util.core.BI to process BigIntegers while
//   signing and verifying signatures. Needed to eliminate size
//   uncertainties when converting BigInteger to/from byte arrays.
// + added tests for null objects in initInternal() and engineInitSign()
//   methods.
// + changed the AlgId semantics to align with RSA implementations.
//
// Revision 1.1  1997/12/07 06:37:27  hopwood
// + Major overhaul of ElGamal to match RSA.
//
// Revision 1.1.1.1.1  1997/11/22  hopwood
// + Renamed this class to Any_RSA_PKCS1Signature from
//   RawElGamalSignature.
//
// Revision 1.1.1.1  1997/11/03 22:36:56  hopwood
// + Imported to CVS (tagged as 'start').
//
// $Endlog$
/*
 * Copyright (c) 1997 Systemics Ltd
 * on behalf of the Cryptix Development Team.  All rights reserved.
 */

package cryptix.provider.elgamal;

import cryptix.CryptixException;
import cryptix.util.core.BI;
import cryptix.util.core.Debug;
import cryptix.util.core.Hex;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.Random;
import java.security.Signature;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.security.PublicKey;
import java.security.PrivateKey;
import java.security.SignatureException;
import java.security.InvalidKeyException;
import java.security.InvalidParameterException;
import xjava.security.interfaces.ElGamalPublicKey;
import xjava.security.interfaces.ElGamalPrivateKey;

/**
 * An abstract class to digest a message and sign/verify the resulting
 * hash value, using any JCA MessageDigest algorithm with the ElGamal
 * digital signature scheme, and formatting and padding conventions
 * based on PKCS#1.
 * <p>
 * <b>References:</b>
 * <ol>
 *   <li> <a href="mailto:[e-mail]">Bruce Schneier</a>,
 *        "Section 19.6 ElGamal,"
 *        <cite>Applied Cryptography, 2nd edition</cite>,
 *        John Wiley &amp; Sons, 1996.
 *        <p>
 *   <li> PKCS#1
 *        An RSA Laboratories Technical Note<br>
 *        Version 1.5<br>
 *        Revised November 1, 1993<br>
 *        An "RSA Data Security, Inc. Public-Key Cryptography Standard (PKCS)"
 * </ol>
 * <p>
 * <b>$Revision: 1.1.1.1 $</b>
 * @author David Hopwood
 * @since  Cryptix 2.2.2
 *
 * @see java.security.interfaces.ElGamalKey
 * @see ElGamalCipher
 * @see java.security.Signature
 */
public abstract class Any_ElGamal_PKCS1Signature
extends Signature
{

// Debugging methods and vars.
//............................................................................

    private static final boolean DEBUG = Debug.GLOBAL_DEBUG;
    private static final int debuglevel =
        DEBUG ? Debug.getLevel("ElGamal", "Any_ElGamal_PKCS1Signature") : 0;
    private static final PrintWriter err = DEBUG ? Debug.getOutput() : null;
    private static void debug(String s) { err.println("Any_ElGamal_PKCS1Signature: " + s); }


// Constants and variables
//............................................................................

    /**
     * The minimum length of <i>p</i> in bits.
     */
    private static final int MIN_BITLENGTH = 256;

    private static final int POSITIVE = 1;
    private static final BigInteger ZERO = BigInteger.valueOf(0);
    private static final BigInteger ONE = BigInteger.valueOf(1);

    private BigInteger p;
    private BigInteger g;
    private BigInteger x; // null if the state is ENCRYPT
    private BigInteger y;

    private int primeLen;
    private Random rng;

    private MessageDigest md;


// Constructor
//............................................................................

    /**
     * Constructor for an Any_ElGamal_PKCS1Signature.
     *
     * @param  mdAlgorithm  the standard JCA algorithm name of the message
     *                      digest to be used.
     */
    protected Any_ElGamal_PKCS1Signature (String mdAlgorithm) {
        super(mdAlgorithm + "/ElGamal/PKCS#1");
        try { md = MessageDigest.getInstance(mdAlgorithm); }
        catch (Exception e) {
            throw new CryptixException(getAlgorithm() +
                ": Unable to instantiate the " + mdAlgorithm +
                " MessageDigest\n" + e);
        }
    }


// Signature abstract methods implementation
//............................................................................

    /**
     * <b>SPI</b>: Initializes the cipher for signing, using the
     * given private key. The key object must implement
     * java.security.interfaces.ElGamalPrivateKey.
     * <p>
     * The input to this algorithm will be padded on the left with random
     * bits, up to the size of a block, before signing.
     *
     * @param key   the private key
     * @exception InvalidKeyException if !(key instanceof
     *          java.security.interfaces.ElGamalPrivateKey)
     */
    protected void engineInitSign(PrivateKey key) throws InvalidKeyException {
        if (!(key instanceof ElGamalPrivateKey))
            throw new InvalidKeyException("ElGamal: signing key does not implement java.security.interfaces.ElGamalPrivateKey");

        ElGamalPrivateKey privateKey = (ElGamalPrivateKey) key;
        BigInteger newX = privateKey.getX();
        if (newX == null) throw new InvalidKeyException("ElGamal: getX() == null");

        initInternal(privateKey.getP(), privateKey.getG(),
                     newX, privateKey.getY());
        if (rng == null)
            rng = new SecureRandom();
    }

    /**
     * <b>SPI</b>: Initializes the cipher for verification, using the
     * given public key. The key object must implement
     * java.security.interfaces.ElGamalPublicKey.
     *
     * @param key   the public key
     * @exception InvalidKeyException if !(key instanceof
     *          java.security.interfaces.ElGamalPublicKey)
     */
    protected void engineInitVerify(PublicKey key) throws InvalidKeyException {
        if (!(key instanceof ElGamalPublicKey))
            throw new InvalidKeyException("ElGamal: verification key does not implement java.security.interfaces.ElGamalPublicKey");

        ElGamalPublicKey publicKey = (ElGamalPublicKey) key;
        initInternal(publicKey.getP(), publicKey.getG(),
                     null, publicKey.getY());
        if (rng == null)
            rng = new SecureRandom();
    }

    private void initInternal(BigInteger newP, BigInteger newG,
                              BigInteger newX, BigInteger newY)
            throws InvalidKeyException{
        if (newP == null) throw new InvalidKeyException("ElGamal: getP() == null");
        if (newG == null) throw new InvalidKeyException("ElGamal: getG() == null");
        if (newY == null) throw new InvalidKeyException("ElGamal: getY() == null");
        if (newP.bitLength() < MIN_BITLENGTH)
            throw new InvalidKeyException("ElGamal: getP().bitLength() < " + MIN_BITLENGTH);

        if (newP.compareTo(ONE) <= 0)
            throw new InvalidKeyException("ElGamal: getP() < 2");

        p = newP;
        g = newG;
        x = newX;
        y = newY;

        primeLen = (p.bitLength() + 7) / 8;
        md.reset();
    }

    /**
     * Updates the data to be signed or verified, using one byte.
     *
     * @param  b  the byte to use for the update process.
     * @exception SignatureException if the engine is not initialised properly.
     */
    protected void engineUpdate (byte b)
    throws SignatureException {
        if (state != VERIFY && state != SIGN)
            throw new SignatureException(getAlgorithm() + ": Not initialized");

        md.update(b);
    }

    /**
     * Updates the data to be signed or verified, using the specified
     * sub-array of bytes, starting at the specified offset.
     *
     * @param  in      the array of bytes.
     * @param  offset  the offset to start from in <i>in</i>.
     * @param  length  the number of bytes to use, starting at <i>offset</i>.
     * @exception SignatureException if the engine is not initialised properly.
     */
    protected void engineUpdate (byte[] in, int offset, int length)
    throws SignatureException {
        if (state != VERIFY && state != SIGN)
            throw new SignatureException(getAlgorithm() + ": Not initialized");

        md.update(in, offset, length);