Java加密技术(五)
接下来我们分析DH加密算法,一种适基于密钥一致协议的加密算法。
DH
Diffie-Hellman算法(D-H算法),密钥一致协议。是由公开密钥密码*的奠基人Diffie和Hellman所提出的一种思想。简单的说就是允许两名用户在公开媒体上交换信息以生成"一致"的、可以共享的密钥。换句话说,就是由甲方产出一对密钥(公钥、私钥),乙方依照甲方公钥产生乙方密钥对(公钥、私钥)。以此为基线,作为数据传输保密基础,同时双方使用同一种对称加密算法构建本地密钥(SecretKey)对数据加密。这样,在互通了本地密钥(SecretKey)算法后,甲乙双方公开自己的公钥,使用对方的公钥和刚才产生的私钥加密数据,同时可以使用对方的公钥和自己的私钥对数据解密。不单单是甲乙双方两方,可以扩展为多方共享数据通讯,这样就完成了网络交互数据的安全通讯!该算法源于中国的同余定理——中国馀数定理。
流程分析:
1.甲方构建密钥对儿,将公钥公布给乙方,将私钥保留;双方约定数据加密算法;乙方通过甲方公钥构建密钥对儿,将公钥公布给甲方,将私钥保留。
2.甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥加密数据,发送给乙方加密后的数据;乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥对数据解密。
3.乙方使用私钥、甲方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥加密数据,发送给甲方加密后的数据;甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥,然后通过本地密钥对数据解密。
通过java代码实现如下:Coder类见 Java加密技术(一)
- import java.security.Key;
- import java.security.KeyFactory;
- import java.security.KeyPair;
- import java.security.KeyPairGenerator;
- import java.security.PublicKey;
- import java.security.spec.PKCS8EncodedKeySpec;
- import java.security.spec.X509EncodedKeySpec;
- import java.util.HashMap;
- import java.util.Map;
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- import javax.crypto.Cipher;
- import javax.crypto.KeyAgreement;
- import javax.crypto.SecretKey;
- import javax.crypto.interfaces.DHPrivateKey;
- import javax.crypto.interfaces.DHPublicKey;
- import javax.crypto.spec.DHParameterSpec;
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- public abstract class DHCoder extends Coder {
- public static final String ALGORITHM = "DH";
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- private static final int KEY_SIZE = 1024;
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- public static final String SECRET_ALGORITHM = "DES";
- private static final String PUBLIC_KEY = "DHPublicKey";
- private static final String PRIVATE_KEY = "DHPrivateKey";
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- public static Map<String, Object> initKey() throws Exception {
- KeyPairGenerator keyPairGenerator = KeyPairGenerator
- .getInstance(ALGORITHM);
- keyPairGenerator.initialize(KEY_SIZE);
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- KeyPair keyPair = keyPairGenerator.generateKeyPair();
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- DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
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- DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
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- Map<String, Object> keyMap = new HashMap<String, Object>(2);
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- keyMap.put(PUBLIC_KEY, publicKey);
- keyMap.put(PRIVATE_KEY, privateKey);
- return keyMap;
- }
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- public static Map<String, Object> initKey(String key) throws Exception {
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- byte[] keyBytes = decryptBASE64(key);
- X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
- KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
- PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
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- DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();
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- KeyPairGenerator keyPairGenerator = KeyPairGenerator
- .getInstance(keyFactory.getAlgorithm());
- keyPairGenerator.initialize(dhParamSpec);
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- KeyPair keyPair = keyPairGenerator.generateKeyPair();
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- DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
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- DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
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- Map<String, Object> keyMap = new HashMap<String, Object>(2);
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- keyMap.put(PUBLIC_KEY, publicKey);
- keyMap.put(PRIVATE_KEY, privateKey);
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- return keyMap;
- }
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- public static byte[] encrypt(byte[] data, String publicKey,
- String privateKey) throws Exception {
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- SecretKey secretKey = getSecretKey(publicKey, privateKey);
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- Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
- cipher.init(Cipher.ENCRYPT_MODE, secretKey);
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- return cipher.doFinal(data);
- }
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- public static byte[] decrypt(byte[] data, String publicKey,
- String privateKey) throws Exception {
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- SecretKey secretKey = getSecretKey(publicKey, privateKey);
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- Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
- cipher.init(Cipher.DECRYPT_MODE, secretKey);
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- return cipher.doFinal(data);
- }
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