一、概述
Diffie-Hellman算法(D-H算法)，密钥一致协议。是由公开密钥密码体制的奠基人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。即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。
二、模型分析
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。
实例：
Java代码 复制代码 收藏代码
1.package cn.tzz.java.crypto.dh;
2.
3.import java.io.IOException;
4.import java.security.Key;
5.import java.security.KeyFactory;
6.import java.security.KeyPair;
7.import java.security.KeyPairGenerator;
8.import java.security.PublicKey;
9.import java.security.spec.PKCS8EncodedKeySpec;
10.import java.security.spec.X509EncodedKeySpec;
11.import java.util.HashMap;
12.import java.util.Map;
13.
14.import javax.crypto.Cipher;
15.import javax.crypto.KeyAgreement;
16.import javax.crypto.SecretKey;
17.import javax.crypto.interfaces.DHPrivateKey;
18.import javax.crypto.interfaces.DHPublicKey;
19.import javax.crypto.spec.DHParameterSpec;
20.import sun.misc.BASE64Decoder;
21.import sun.misc.BASE64Encoder;
22.import org.junit.Test;
23.
24.
25.public class DHUtil {
26.
27. public static final String ALGORITHM = "DH";
28. /**默认密钥字节数*/
29. private static final int KEY_SIZE = 1024;
30.
31. /** DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法*/
32. public static final String SECRET_ALGORITHM = "DES";
33. private static final String PUBLIC_KEY = "DHPublicKey";//公钥
34. private static final String PRIVATE_KEY = "DHPrivateKey";//私钥
35.
36. public String encryptBASE64(byte[] key) {
37. return (new BASE64Encoder()).encodeBuffer(key);
38. }
39.
40. public byte[] decryptBASE64(String key) throws IOException {
41. return new BASE64Decoder().decodeBuffer(key);
42. }
43.
44. /** 初始化甲方密钥 */
45. public Map<String, Object> initKey() throws Exception {
46. KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
47. keyPairGenerator.initialize(KEY_SIZE);
48. KeyPair keyPair = keyPairGenerator.generateKeyPair();
49. // 甲方公钥
50. DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
51. // 甲方私钥
52. DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
53. Map<String, Object> keyMap = new HashMap<String, Object>(2);
54. keyMap.put(PUBLIC_KEY, publicKey);
55. keyMap.put(PRIVATE_KEY, privateKey);
56. return keyMap;
57. }
58.
59. /**初始化乙方密钥*/
60. public Map<String, Object> initKey(String key) throws Exception {
61. // 解析甲方公钥
62. byte[] keyBytes = decryptBASE64(key);
63. X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
64. KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
65. PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
66. // 由甲方公钥构建乙方密钥
67. DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();
68. KeyPairGenerator keyPairGenerator = KeyPairGenerator
69. .getInstance(keyFactory.getAlgorithm());
70. keyPairGenerator.initialize(dhParamSpec);
71. KeyPair keyPair = keyPairGenerator.generateKeyPair();
72. // 乙方公钥
73. DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();
74. // 乙方私钥
75. DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();
76. Map<String, Object> keyMap = new HashMap<String, Object>(2);
77. keyMap.put(PUBLIC_KEY, publicKey);
78. keyMap.put(PRIVATE_KEY, privateKey);
79.
80. return keyMap;
81. }
82.
83. /**
84. * 加密<br>
85. *
86. * @param data
87. * 待加密数据
88. * @param publicKey
89. * 甲方公钥
90. * @param privateKey
91. * 乙方私钥
92. * @return
93. * @throws Exception
94. */
95. public byte[] encrypt(byte[] data, String publicKey, String privateKey) throws Exception {
96. // 生成本地密钥
97. SecretKey secretKey = getSecretKey(publicKey, privateKey);
98. // 数据加密
99. Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
100. cipher.init(Cipher.ENCRYPT_MODE, secretKey);
101. return cipher.doFinal(data);
102. }
103.
104. /**
105. * 解密<br>
106. *
107. * @param data
108. * 待解密数据
109. * @param publicKey
110. * 乙方公钥
111. * @param privateKey
112. * 乙方私钥
113. * @return
114. * @throws Exception
115. */
116. public byte[] decrypt(byte[] data, String publicKey, String privateKey) throws Exception {
117. // 生成本地密钥
118. SecretKey secretKey = getSecretKey(publicKey, privateKey);
119. // 数据解密
120. Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
121. cipher.init(Cipher.DECRYPT_MODE, secretKey);
122. return cipher.doFinal(data);
123. }
124.
125. /**构建密钥*/
126. private SecretKey getSecretKey(String publicKey, String privateKey) throws Exception {
127. // 初始化公钥
128. byte[] pubKeyBytes = decryptBASE64(publicKey);
129. KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
130. X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(pubKeyBytes);
131. PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
132.
133. // 初始化私钥
134. byte[] priKeyBytes = decryptBASE64(privateKey);
135.
136. PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(priKeyBytes);
137. Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);
138.
139. KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory
140. .getAlgorithm());
141. keyAgree.init(priKey);
142. keyAgree.doPhase(pubKey, true);
143.
144. // 生成本地密钥
145. SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);
146. return secretKey;
147. }
148.
149. /** 取得私钥*/
150. public String getPrivateKey(Map<String, Object> keyMap) throws Exception {
151. Key key = (Key) keyMap.get(PRIVATE_KEY);
152. return encryptBASE64(key.getEncoded());
153. }
154.
155. /**取得公钥*/
156. public String getPublicKey(Map<String, Object> keyMap) throws Exception {
157. Key key = (Key) keyMap.get(PUBLIC_KEY);
158. return encryptBASE64(key.getEncoded());
159. }
160.
161. @Test
162. public void testDH() throws Exception {
163. // 生成甲方密钥对儿
164. Map<String, Object> aKeyMap = initKey();
165. String aPublicKey = getPublicKey(aKeyMap);
166. String aPrivateKey = getPrivateKey(aKeyMap);
167. System.out.println("甲方公钥:\r" + aPublicKey);
168. System.out.println("甲方私钥:\r" + aPrivateKey);
169.
170. // 由甲方公钥产生本地密钥对儿
171. Map<String, Object> bKeyMap = initKey(aPublicKey);
172. String bPublicKey = getPublicKey(bKeyMap);
173. String bPrivateKey = getPrivateKey(bKeyMap);
174. System.out.println("乙方公钥:\r" + bPublicKey);
175. System.out.println("乙方私钥:\r" + bPrivateKey);
176.
177. String aInput = "abcdef ";
178. System.out.println("原文: " + aInput);
179.
180. // 由甲方公钥，乙方私钥构建密文
181. byte[] aCode = encrypt(aInput.getBytes(), aPublicKey, bPrivateKey);
182.
183. // 由乙方公钥，甲方私钥解密
184. byte[] aDecode = decrypt(aCode, bPublicKey, aPrivateKey);
185. String aOutput = (new String(aDecode));
186. System.out.println("解密: " + aOutput);
187.
188. /**反过来加密解密*/
189. String bInput = "123456 ";
190. System.out.println("原文: " + bInput);
191.
192. // 由乙方公钥，甲方私钥构建密文
193. byte[] bCode = encrypt(bInput.getBytes(), bPublicKey, aPrivateKey);
194.
195. // 由甲方公钥，乙方私钥解密
196. byte[] bDecode = decrypt(bCode, aPublicKey, bPrivateKey);
197. String bOutput = (new String(bDecode));
198. System.out.println("解密: " + bOutput);
199. }
200.
201.}
java的非对称加密算法
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转载自weitao1026.iteye.com/blog/2266325
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