RSA 数据加密和数字签名算法

 package com.ice.webos.util.security;

 import java.math.BigInteger;
 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 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。<br>
  * RSA同时有两把钥匙，公钥与私钥。同时支持数字签名。<br>
  * 数字签名的意义在于，对传输过来的数据进行校验。确保数据在传输过程中不被修改。
  * <ul>
  * 流程分析：
  * <li>甲方构建密钥对儿，将公钥公布给乙方，将私钥保留。</li>
  * <li>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。</li>
  * <li>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。 </li>
  * <ul>
  * 
  * @author Ice_Liu
  * 
  */
 public class RSACryptUtil {
     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 = CryptUtil.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 CryptUtil.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 = CryptUtil.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(CryptUtil.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 = CryptUtil.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 = CryptUtil.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 = CryptUtil.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 = CryptUtil.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 CryptUtil.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 CryptUtil.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;
     }

     /**
      * @param args
 */
     public static void main(String[] args) {
         try {
             PBECryptUtil.main(args);
             System.out.println("****************************************");
             System.out.println("=====RSA加密与解密=====");
             // 初始化公钥,私钥
             Map<String, Object> keyMap = initKey();
             String publicKey = RSACryptUtil.getPublicKey(keyMap);
             String privateKey = RSACryptUtil.getPrivateKey(keyMap);
             System.out.println("公钥: \n\r" + publicKey);
             System.out.println("私钥： \n\r" + privateKey);
             System.out.println("公钥加密——私钥解密");
             String inputStr = "阿伯才的覆盖";
             byte[] data = inputStr.getBytes("UTF-8");
             // 公钥加密
             byte[] encodedData = RSACryptUtil.encryptByPublicKey(data, publicKey);
             System.out.println("公钥加密后:" + new BigInteger(encodedData).toString(32));
             // 私钥解密
             byte[] decodedData = RSACryptUtil.decryptByPrivateKey(encodedData, privateKey);
             String outputStr = new String(decodedData, "UTF-8");
             System.out.println("加密前: " + inputStr);
             System.out.println("解密后: " + outputStr);

             System.out.println("私钥加密——公钥解密");
             // 私钥加密
             encodedData = RSACryptUtil.encryptByPrivateKey(data, privateKey);
             System.out.println("私钥加密后:" + new BigInteger(encodedData).toString(32));
             // 公钥解密
             decodedData = RSACryptUtil.decryptByPublicKey(encodedData, publicKey);
             outputStr = new String(decodedData, "UTF-8");
             System.out.println("加密前: " + inputStr);
             System.out.println("解密后: " + outputStr);

             System.out.println("私钥签名——公钥验证签名");
             // 使用私钥产生签名
             String sign = RSACryptUtil.sign(encodedData, privateKey);
             System.out.println("签名:" + sign);
             // 使用公匙验证签名
             boolean status = RSACryptUtil.verify(encodedData, publicKey, sign);
             System.err.println("验证签名结果:" + status);
         } catch (Exception e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

     }

 }

转自：http://www.cnblogs.com/liubin0509/archive/2012/01/29/2331075.html