Java Cryptography

Adding the ElGamal Classes

In this chapter, we’ll develop a full suite of classes to support ElGamal signatures and ciphers. The Jonathan provider will need to know about some of the implementation classes, namely:

oreilly.jonathan.crypto.ElGamalKeyPairGenerator
oreilly.jonathan.crypto.ElGamalSignature
oreilly.jonathan.crypto.ElGamalCipher

Thus, we just need to add the correct associations to our simple provider class. It’s a piece of cake:

package oreilly.jonathan.crypto;

import java.security.*;

public class Provider
    extends java.security.Provider {
  public Provider() {
    super ("Jonathan",
        1.2,
        "Jonathan's Cryptography Provider");
    
    put("KeyPairGenerator.ElGamal",
        "oreilly.jonathan.crypto.ElGamalKeyPairGenerator");
    put("Cipher.ElGamal", "oreilly.jonathan.crypto.ElGamalCipher");
    put("Signature.ElGamal", "oreilly.jonathan.crypto.ElGamalSignature");
    
    put("Cipher.DES/CBC/PKCS5Padding",
        "oreilly.jonathan.crypto.CBCWrapper");
    put("Cipher.DES/CFB/NoPadding", "oreilly.jonathan.crypto.CFBWrapper");

put("Alg.Alias.Cipher.DES/CFB8/NoPadding", "DES/CFB/NoPadding");
  }
}

The hard part is actually implementing the algorithms. We’ll spend the rest of the chapter doing just that.