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非对称加密算法是相对于对称加密算法来说的，对于对称加密算法请查阅之前的总结，今天为大家介绍一下DH算法，DH是一种密钥交换算法，接收方根据发送方加密时的密钥，生成接收方解密密钥。下面就一起来学习一下吧：
初始化发送方密钥：
KeyPairGenerator sendKeyPairGenerator = KeyPairGenerator.getInstance("DH");
sendKeyPairGenerator.initialize(512);
KeyPair sendKeyPair = sendKeyPairGenerator.generateKeyPair();
byte[] sendPublicKeyEnc = sendKeyPair.getPublic().getEncoded();//生成发送方公钥，发送给接收方（网络、文件...）
初始化接收方密钥：
KeyFactory receiverKeyFactory = KeyFactory.getInstance("DH");
X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(sendPublicKeyEnc);
PublicKey receivePublicKey = receiverKeyFactory.generatePublic(x509EncodedKeySpec);
DHParameterSpec dhParameterSpec = ((DHPublicKey)receivePublicKey).getParams();
KeyPairGenerator receiverKeyPairGenerator = KeyPairGenerator.getInstance("DH");
receiverKeyPairGenerator.initialize(dhParameterSpec);
KeyPair receiverKeyPair = receiverKeyPairGenerator.generateKeyPair();
PrivateKey receiverPrivateKey = receiverKeyPair.getPrivate();
byte[] receiverPublicKeyEnc = receiverKeyPair.getPublic().getEncoded();
构建接收方密钥：
KeyAgreement receiverKeyAgreement = KeyAgreement.getInstance("DH");
receiverKeyAgreement.init(receiverPrivateKey);
receiverKeyAgreement.doPhase(receivePublicKey, true);
SecretKey receiverDESKey = receiverKeyAgreement.generateSecret("DES");//接收方Key
构建发送方密钥：
KeyFactory sendKeyFactory = KeyFactory.getInstance("DH");
x509EncodedKeySpec = new X509EncodedKeySpec(receiverPublicKeyEnc);
PublicKey sendPublicKey = sendKeyFactory.generatePublic(x509EncodedKeySpec);
KeyAgreement sendKeyAgreement = KeyAgreement.getInstance("DH");
sendKeyAgreement.init(sendKeyPair.getPrivate());
sendKeyAgreement.doPhase(sendPublicKey, true);
SecretKey sendDESKey = sendKeyAgreement.generateSecret("DES");//发送方Key
发送方加密：
Cipher sendCipher = Cipher.getInstance("DES");
sendCipher.init(Cipher.ENCRYPT_MODE, sendDESKey);
byte[] sendResult = sendCipher.doFinal(src.getBytes());
System.out.println("sendResult ："+Hex.encodeHexString(sendResult));
接收方解密：
Cipher receiverCipher = Cipher.getInstance("DES");
receiverCipher.init(Cipher.DECRYPT_MODE, receiverDESKey);
byte[] receiverResult = receiverCipher.doFinal(sendResult);
System.out.println("receiverResult : "+new String (receiverResult));
基于密钥交换的非对称加密算法（DH）,到这里就总结完毕了。
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原文地址：http://www.cnblogs.com/AndroidJotting/p/4290634.html
