Java加密技术 之 RSA

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:
Java代码

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 
 */ 
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 
 * 
 * @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: 
Java代码 收藏代码
import static org.junit.Assert.*; 
 
import org.junit.Before; 
import org.junit.Test; 
 
import java.util.Map; 
 
/** 
 * 
 * @author 梁栋 
 * @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: nr" + publicKey); 
 System.err.println("私钥: nr" + 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 + "nr" + "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 + "nr" + "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); 
 
 } 
 
}

控制台输出:
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。

声明:本文采用 BY-NC-SA 协议进行授权,本文链接:Java加密技术 之 RSA

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