非对称加密算法RSA--转
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：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.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 * @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 * * @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> * 用公钥解密 * * @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 * @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); } }
原文地址：http://snowolf.iteye.com/blog/381767
版权声明：本文为davidwang456原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。