cryptix.provider.elgamal

Class ElGamalAlgorithm

java.lang.Object

cryptix.provider.elgamal.ElGamalAlgorithm

public final class ElGamalAlgorithm
extends java.lang.Object

A class that calculates the ElGamal family of algorithms (encryption, decryption, signing and verification).

References:

1. Bruce Schneier, "Section 19.6 ElGamal," Applied Cryptography, 2nd edition, John Wiley & Sons, 1996.

Copyright © 1997 Systemics Ltd on behalf of the Cryptix Development Team.
All rights reserved.

$Revision: 1.2 $

Since:

Cryptix 2.2.2

Author:

David Hopwood

Method Summary

Modifier and Type	Method and Description
static java.math.BigInteger	decrypt(java.math.BigInteger a, java.math.BigInteger b, java.math.BigInteger p, java.math.BigInteger g, java.math.BigInteger x) The decryption algorithm for ElGamal.
static void	encrypt(java.math.BigInteger M, java.math.BigInteger[] ab, java.math.BigInteger p, java.math.BigInteger g, java.math.BigInteger y, java.util.Random rng) The encryption algorithm for ElGamal.
static void	sign(java.math.BigInteger M, java.math.BigInteger[] ab, java.math.BigInteger p, java.math.BigInteger g, java.math.BigInteger x, java.util.Random rng) The signature algorithm for ElGamal.
static boolean	verify(java.math.BigInteger M, java.math.BigInteger a, java.math.BigInteger b, java.math.BigInteger p, java.math.BigInteger g, java.math.BigInteger y) The verification algorithm for ElGamal.

Methods inherited from class java.lang.Object

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

Method Detail

encrypt

public static void encrypt(java.math.BigInteger M,
                           java.math.BigInteger[] ab,
                           java.math.BigInteger p,
                           java.math.BigInteger g,
                           java.math.BigInteger y,
                           java.util.Random rng)

The encryption algorithm for ElGamal. The two parts of the ciphertext, a and b, will be stored in ab[0] and ab[1] respectively.

Parameters:

M - the plaintext.

ab - a 2-element BigInteger array in which to store the ciphertext.

p - the prime from the public key.

g - the generator from the public key.

y - the value of y from the public key.

rng - a random number generator to be used for encryption.

decrypt

public static java.math.BigInteger decrypt(java.math.BigInteger a,
                                           java.math.BigInteger b,
                                           java.math.BigInteger p,
                                           java.math.BigInteger g,
                                           java.math.BigInteger x)

The decryption algorithm for ElGamal. a and b are the two parts of the ciphertext (using the same convention as given in Schneier).

Parameters:

a - the first part of the ciphertext.

b - the second part of the ciphertext.

p - the prime from the private key.

g - the generator from the private key.

x - the value of x from the private key.

Returns:

the plaintext.

sign

public static void sign(java.math.BigInteger M,
                        java.math.BigInteger[] ab,
                        java.math.BigInteger p,
                        java.math.BigInteger g,
                        java.math.BigInteger x,
                        java.util.Random rng)

The signature algorithm for ElGamal. ab should be a two-element BigInteger array. The two parts of the signature, a and b, will be stored in ab[0] and ab[1] respectively.

Parameters:

M - the value to be signed.

ab - an array in which to store the result.

p - the prime from the private key.

g - the generator from the private key.

x - the value of x from the private key.

rng - a random number generator to be used for signing.

verify

public static boolean verify(java.math.BigInteger M,
                             java.math.BigInteger a,
                             java.math.BigInteger b,
                             java.math.BigInteger p,
                             java.math.BigInteger g,
                             java.math.BigInteger y)

The verification algorithm for ElGamal. Returns true iff the signature was verified successfully.

Parameters:

M - the value that was signed.

a - the first part of the signature.

b - the second part of the signature.

p - the prime from the public key.

g - the generator from the public key.

y - the value of y from the public key.

Returns:

true iff the signature is valid.