加密解密方法MD5/SHA1，DSA，DESede/DES，Diffie-Hellman的使用

package bivin.security; 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.*; 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"); } }