testdhkey.java

用java写的Diffie-Hellman密钥交换协议

import java.io.*;
import java.math.BigInteger;
import java.security.*;
import java.security.spec.*;
import java.security.interfaces.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;
import com.sun.crypto.provider.SunJCE;
public class testDHKey {
    public static void main(String argv[]) {
    try {
        testDHKey my= new testDHKey();
        my.run();
    } catch (Exception e) {
        System.err.println(e);
    }
    }
    private void run() throws Exception {
        Security.addProvider(new com.sun.crypto.provider.SunJCE());
    System.out.println("ALICE: 产生 DH 对 ...");
    KeyPairGenerator aliceKpairGen = KeyPairGenerator.getInstance("DH");
        aliceKpairGen.initialize(512);
    KeyPair aliceKpair = aliceKpairGen.generateKeyPair(); //生成时间长
        // 张三(Alice)生成公共密钥 alicePubKeyEnc 并发送给李四(Bob) ,
        //比如用文件方式,socket.....
    byte[] alicePubKeyEnc = aliceKpair.getPublic().getEncoded();
       //bob接收到alice的编码后的公钥,将其解码
    KeyFactory bobKeyFac = KeyFactory.getInstance("DH");
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec  (alicePubKeyEnc);
    PublicKey alicePubKey = bobKeyFac.generatePublic(x509KeySpec);
        System.out.println("alice公钥bob解码成功");
     // bob必须用相同的参数初始化的他的DH KEY对,所以要从Alice发给他的公开密钥,
         //中读出参数,再用这个参数初始化他的 DH key对
         //从alicePubKye中取alice初始化时用的参数
    DHParameterSpec dhParamSpec = ((DHPublicKey)alicePubKey).getParams();
    KeyPairGenerator bobKpairGen = KeyPairGenerator.getInstance("DH");
    bobKpairGen.initialize(dhParamSpec);
    KeyPair bobKpair = bobKpairGen.generateKeyPair();
        System.out.println("BOB: 生成 DH key 对成功");
    KeyAgreement bobKeyAgree = KeyAgreement.getInstance("DH");
    bobKeyAgree.init(bobKpair.getPrivate());
        System.out.println("BOB: 初始化本地key成功");
        //李四(bob) 生成本地的密钥 bobDesKey
    bobKeyAgree.doPhase(alicePubKey, true);
    SecretKey bobDesKey = bobKeyAgree.generateSecret("DES");
    System.out.println("BOB: 用alice的公钥定位本地key,生成本地DES密钥成功");
        // Bob生成公共密钥 bobPubKeyEnc 并发送给Alice,
        //比如用文件方式,socket.....,使其生成本地密钥
    byte[] bobPubKeyEnc = bobKpair.getPublic().getEncoded();
        System.out.println("BOB向ALICE发送公钥");
         // alice接收到 bobPubKeyEnc后生成bobPubKey
         // 再进行定位,使aliceKeyAgree定位在bobPubKey
    KeyFactory aliceKeyFac = KeyFactory.getInstance("DH");
    x509KeySpec = new X509EncodedKeySpec(bobPubKeyEnc);
    PublicKey bobPubKey = aliceKeyFac.generatePublic(x509KeySpec);
       System.out.println("ALICE接收BOB公钥并解码成功");
;
    KeyAgreement aliceKeyAgree = KeyAgreement.getInstance("DH");
    aliceKeyAgree.init(aliceKpair.getPrivate());
        System.out.println("ALICE: 初始化本地key成功");
    aliceKeyAgree.doPhase(bobPubKey, true);
        // 张三(alice) 生成本地的密钥 aliceDesKey
    SecretKey aliceDesKey = aliceKeyAgree.generateSecret("DES");
        System.out.println("ALICE: 用bob的公钥定位本地key,并生成本地DES密钥");
        if (aliceDesKey.equals(bobDesKey)) System.out.println("张三和李四的密钥相同");
       //现在张三和李四的本地的deskey是相同的所以,完全可以进行发送加密,接收后解密,达到
       //安全通道的的目的
        /*
         * bob用bobDesKey密钥加密信息
         */
    Cipher bobCipher = Cipher.getInstance("DES");
    bobCipher.init(Cipher.ENCRYPT_MODE, bobDesKey);
        String bobinfo= "这是李四的机密信息";
        System.out.println("李四加密前原文:"+bobinfo);
    byte[] cleartext =bobinfo.getBytes();
    byte[] ciphertext = bobCipher.doFinal(cleartext);
        /*
         * alice用aliceDesKey密钥解密
         */
    Cipher aliceCipher = Cipher.getInstance("DES");
    aliceCipher.init(Cipher.DECRYPT_MODE, aliceDesKey);
    byte[] recovered = aliceCipher.doFinal(ciphertext);
        System.out.println("alice解密bob的信息:"+(new String(recovered)));
    if (!java.util.Arrays.equals(cleartext, recovered))
        throw new Exception("解密后与原文信息不同");
    System.out.println("解密后相同");
    }
}