漫谈Java加密技术（四）

RSA
这种算法1978年就出现了，它是第一个既能用于数据加密也能用于数字签名的算法。它易于理解和操作，也很流行。算法的名字以发明者的名字命名：Ron Rivest, AdiShamir 和Leonard Adleman。
这种加密算法的特点主要是密钥的变化，上文我们看到DES只有一个密钥。相当于只有一把钥匙，如果这把钥匙丢了，数据也就不安全了。RSA同时有两把钥匙，公钥与私钥。同时支持数字签名。数字签名的意义在于，对传输过来的数据进行校验。确保数据在传输工程中不被修改。

流程分析：

甲方构建密钥对儿，将公钥公布给乙方，将私钥保留。
甲方使用私钥加密数据，然后用私钥对加密后的数据签名，发送给乙方签名以及加密后的数据；乙方使用公钥、签名来验证待解密数据是否有效，如果有效使用公钥对数据解密。
乙方使用公钥加密数据，向甲方发送经过加密后的数据；甲方获得加密数据，通过私钥解密。

按如上步骤给出序列图，如下：

通过java代码实现如下：

import java.security.Key;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.Signature;

import java.security.interfaces.RSAPrivateKey;

import java.security.interfaces.RSAPublicKey;

import java.security.spec.PKCS8EncodedKeySpec;

import java.security.spec.X509EncodedKeySpec;

import java.util.HashMap;

import java.util.Map;

import javax.crypto.Cipher;

/**

* RSA安全编码组件

* @author 梁栋 http://www.bt285.cn http://www.5a520.cn

* @version 1.0

* @since 1.0

public abstract class RSACoder extends Coder {

public static final String KEY_ALGORITHM = "RSA";

public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

private static final String PUBLIC_KEY = "RSAPublicKey";

private static final String PRIVATE_KEY = "RSAPrivateKey";

/**

* 用私钥对信息生成数字签名

* @param data

* 加密数据

* @param privateKey

* 私钥

* @return

* @throws Exception

public static String sign(byte[] data, String privateKey) throws Exception {

// 解密由base64编码的私钥

byte[] keyBytes = decryptBASE64(privateKey);

// 构造PKCS8EncodedKeySpec对象

PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

// KEY_ALGORITHM 指定的加密算法

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

// 取私钥匙对象

PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

// 用私钥对信息生成数字签名

Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);

signature.initSign(priKey);

signature.update(data);

return encryptBASE64(signature.sign());

}

/**

* 校验数字签名

* @param data

* 加密数据

* @param publicKey

* 公钥

* @param sign

* 数字签名

* @return 校验成功返回true 失败返回false

* @throws Exception

public static boolean verify(byte[] data, String publicKey, String sign)

throws Exception {

// 解密由base64编码的公钥

byte[] keyBytes = decryptBASE64(publicKey);

// 构造X509EncodedKeySpec对象

X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

// KEY_ALGORITHM 指定的加密算法

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

// 取公钥匙对象

PublicKey pubKey = keyFactory.generatePublic(keySpec);

Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);

signature.initVerify(pubKey);

signature.update(data);

// 验证签名是否正常

return signature.verify(decryptBASE64(sign));

}

/**

* 解密<br>

* 用私钥解密 http://www.5a520.cn http://www.feng123.com

* @param data

* @param key

* @return

* @throws Exception

public static byte[] decryptByPrivateKey(byte[] data, String key)

throws Exception {

// 对密钥解密

byte[] keyBytes = decryptBASE64(key);

// 取得私钥

PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

// 对数据解密

Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.DECRYPT_MODE, privateKey);

return cipher.doFinal(data);

}

/**

* 解密<br>

* 用私钥解密

* @param data

* @param key

* @return

* @throws Exception

public static byte[] decryptByPublicKey(byte[] data, String key)

throws Exception {

// 对密钥解密

byte[] keyBytes = decryptBASE64(key);

// 取得公钥

X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

Key publicKey = keyFactory.generatePublic(x509KeySpec);

// 对数据解密

Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.DECRYPT_MODE, publicKey);

return cipher.doFinal(data);

}

/**

* 加密<br>

* 用公钥加密

* @param data

* @param key

* @return

* @throws Exception

public static byte[] encryptByPublicKey(byte[] data, String key)

throws Exception {

// 对公钥解密

byte[] keyBytes = decryptBASE64(key);

// 取得公钥

X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

Key publicKey = keyFactory.generatePublic(x509KeySpec);

// 对数据加密

Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.ENCRYPT_MODE, publicKey);

return cipher.doFinal(data);

}

/**

* 加密<br>

* 用私钥加密

* @param data

* @param key

* @return

* @throws Exception

public static byte[] encryptByPrivateKey(byte[] data, String key)

throws Exception {

// 对密钥解密

byte[] keyBytes = decryptBASE64(key);

// 取得私钥

PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

// 对数据加密

Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

cipher.init(Cipher.ENCRYPT_MODE, privateKey);

return cipher.doFinal(data);

}

/**

* 取得私钥

* @param keyMap

* @return

* @throws Exception

public static String getPrivateKey(Map<String, Object> keyMap)

throws Exception {

Key key = (Key) keyMap.get(PRIVATE_KEY);

return encryptBASE64(key.getEncoded());

}

/**

* 取得公钥

* @param keyMap

* @return

* @throws Exception

public static String getPublicKey(Map<String, Object> keyMap)

throws Exception {

Key key = (Key) keyMap.get(PUBLIC_KEY);

return encryptBASE64(key.getEncoded());

}

/**

* 初始化密钥

* @return

* @throws Exception

public static Map<String, Object> initKey() throws Exception {

KeyPairGenerator keyPairGen = KeyPairGenerator

.getInstance(KEY_ALGORITHM);

keyPairGen.initialize(1024);

KeyPair keyPair = keyPairGen.generateKeyPair();

// 公钥

RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

// 私钥

RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

Map<String, Object> keyMap = new HashMap<String, Object>(2);

keyMap.put(PUBLIC_KEY, publicKey);

keyMap.put(PRIVATE_KEY, privateKey);

return keyMap;

}

再给出一个测试类：

import static org.junit.Assert.*;

import org.junit.Before;

import org.junit.Test;

import java.util.Map;

/**

* @author 梁栋 http://www.bt285.cn http://www.guihua.org

* @version 1.0

* @since 1.0

public class RSACoderTest {

private String publicKey;

private String privateKey;

@Before

public void setUp() throws Exception {

Map<String, Object> keyMap = RSACoder.initKey();

publicKey = RSACoder.getPublicKey(keyMap);

privateKey = RSACoder.getPrivateKey(keyMap);

System.err.println("公钥: \n\r" + publicKey);

System.err.println("私钥： \n\r" + privateKey);

}

@Test

public void test() throws Exception {

System.err.println("公钥加密——私钥解密");

String inputStr = "abc";

byte[] data = inputStr.getBytes();

byte[] encodedData = RSACoder.encryptByPublicKey(data, publicKey);

byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData,

privateKey);

String outputStr = new String(decodedData);

System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);

assertEquals(inputStr, outputStr);

}

@Test

public void testSign() throws Exception {

System.err.println("私钥加密——公钥解密");

String inputStr = "sign";

byte[] data = inputStr.getBytes();

byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);

byte[] decodedData = RSACoder

.decryptByPublicKey(encodedData, publicKey);

String outputStr = new String(decodedData);

System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);

assertEquals(inputStr, outputStr);

System.err.println("私钥签名——公钥验证签名");

// 产生签名

String sign = RSACoder.sign(encodedData, privateKey);

System.err.println("签名:\r" + sign);

// 验证签名

boolean status = RSACoder.verify(encodedData, publicKey, sign);

System.err.println("状态:\r" + status);

assertTrue(status);

}

Console代码:

公钥:
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCYU/+I0+z1aBl5X6DUUOHQ7FZpmBSDbKTtx89J
EcB64jFCkunELT8qiKly7fzEqD03g8ALlu5XvX+bBqHFy7YPJJP0ekE2X3wjUnh2NxlqpH3/B/xm
1ZdSlCwDIkbijhBVDjA/bu5BObhZqQmDwIxlQInL9oVz+o6FbAZCyHBd7wIDAQAB
私钥：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公钥加密——私钥解密
加密前: abc
解密后: abc
公钥:
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDdOj40yEB48XqWxmPILmJAc7UecIN7F32etSHF
9rwbuEh3+iTPOGSxhoSQpOED0vOb0ZIMkBXZSgsxLaBSin2RZ09YKWRjtpCA0kDkiD11gj4tzTiM
l9qq1kwSK7ZkGAgodEn3yIILVmQDuEImHOXFtulvJ71ka07u3LuwUNdB/wIDAQAB
私钥：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私钥加密——公钥解密
加密前: sign
解密后: sign
私钥签名——公钥验证签名
签名:
ud1RsIwmSC1pN22I4IXteg1VD2FbiehKUfNxgVSHzvQNIK+d20FCkHCqh9djP3h94iWnIUY0ifU+
mbJkhAl/i5krExOE0hknOnPMcEP+lZV1RbJI2zG2YooSp2XDleqrQk5e/QF2Mx0Zxt8Xsg7ucVpn
i3wwbYWs9wSzIf0UjlM=
状态:
true

简要总结一下，使用公钥加密、私钥解密，完成了乙方到甲方的一次数据传递，通过私钥加密、公钥解密，同时通过私钥签名、公钥验证签名，完成了一次甲方到乙方的数据传递与验证，两次数据传递完成一整套的数据交互！

类似数字签名，数字信封是这样描述的：

数字信封
　　数字信封用加密技术来保证只有特定的收信人才能阅读信的内容。
流程：
信息发送方采用对称密钥来加密信息，然后再用接收方的公钥来加密此对称密钥（这部分称为数字信封），再将它和信息一起发送给接收方；接收方先用相应的私钥打开数字信封，得到对称密钥，然后使用对称密钥再解开信息。

posted on 2009-07-09 21:08 bitmap 阅读(1227) 评论(0) 编辑收藏

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