RSA加解密

以下是利用rsa技术进行加解密的示例，rsa是非对称密钥，利用公钥加密，私钥解密

1、生成密钥对

/*	
 * 
 * All rights reserved.
 *			 
 * Contributors:
 *    teng_srong - initial API and implementation
 * 
 */

package com.test.spell.rsa;

import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;

/**
 * 
 * 描述：<p>&nbsp;&nbsp;&nbsp;&nbsp; 产生公钥和私钥对，并且保存在文件中，公钥 pk.dat，私钥 sk.dat。</p>
 * 创建日期：2012-6-26 下午5:31:44<br>
 * @author：teng_srong<br> 
 * @update：$Date$<br>
 * @version：$Revision$<br>
 * @since 版本号，用来指定该类是从整个项目的哪个版本开始加入到项目中的
 */
public class KeyGen {

	/**
	  * @param args
	  * @throws Exception
	  */
	 public static void main(String[] args) throws Exception {
	  // 加密的种子信息
	  String keyInfo = "ASDFSDFNUGD__TYTY";
	  KeyGen kg = new KeyGen();
	  kg.genKeys(keyInfo);
	 }

	 /**
	  * 根据keyInfo产生公钥和私钥，并且保存到pk.dat和sk.dat文件中
	  *
	  * @param keyInfo
	  * @throws Exception
	  */
	 public void genKeys(String keyInfo) throws Exception {
	  KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA");
	  SecureRandom random = new SecureRandom();
	  random.setSeed(keyInfo.getBytes());
	  // 初始加密，长度为512，必须是大于512才可以的
	  keygen.initialize(512, random);
	  // 取得密钥对
	  KeyPair kp = keygen.generateKeyPair();
	  // 取得公钥
	  PublicKey publicKey = kp.getPublic();
	  System.out.println(publicKey);
	  saveFile(publicKey, "pk.dat");
	  // 取得私钥
	  PrivateKey privateKey = kp.getPrivate();
	  saveFile(privateKey, "sk.dat");

	 }

	 /**
	  * 保存对象到文件
	  *
	  * @param obj
	  * @param fileName
	  * @throws Exception
	  */
	 private void saveFile(Object obj, String fileName) throws Exception {
	  ObjectOutputStream output = new ObjectOutputStream(
	   new FileOutputStream(fileName));
	  output.writeObject(obj);
	  output.close();
	 }

}

 2、加解密过程

/*	
 * 
 * All rights reserved.
 *			 
 * Contributors:
 *    teng_srong - initial API and implementation
 * 
 */

package com.test.spell.rsa;

import java.io.FileInputStream;
import java.io.ObjectInputStream;
import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
//import java.util.Scanner;

import javax.crypto.Cipher;

/**
 * 
 * 描述：<p>&nbsp;&nbsp;&nbsp;&nbsp;功能描述,该部分必须以中文句号结尾。</p>
 * 创建日期：2012-6-26 下午5:34:25<br>
 * @author：teng_srong<br> 
 * @update：$Date$<br>
 * @version：$Revision$<br>
 * @since 版本号，用来指定该类是从整个项目的哪个版本开始加入到项目中的
 */
public class RsaMessage {

	/**
	 * @param args
	 * @throws Exception 
	 */
	public static void main(String[] args) throws Exception {

		  String str = "hello,我是中国人";
		  System.out.println("原文：" + str);
//		  Scanner scanner=newr.next();

		  RsaMessage rsa = new RsaMessage();
		  RSAPrivateKey privateKey = (RSAPrivateKey) rsa.readFromFile("sk.dat");
		  RSAPublicKey publickKey = (RSAPublicKey) rsa.readFromFile("pk.dat");

		  byte[] encbyte = rsa.encrypt(str, privateKey);
		  System.out.println("私钥加密后：");
		  String encStr = toHexString(encbyte);
		  System.out.println(encStr);

		  byte[] signBytes = rsa.sign(str, privateKey);
		  System.out.println("签名值：");
		  String signStr = toHexString(signBytes);
		  System.out.println(signStr);

		  byte[] decByte = rsa.decrypt(encStr, publickKey);
		  System.out.println("公钥解密后：");
		  String decStr = new String(decByte);
		  System.out.println(decStr);

		  if (rsa.verifySign(str, signStr, publickKey)) {
		   System.out.println("rsa sign check success");
		  } else {
		   System.out.println("rsa sign check failure");
		  }
	}
	 /**
	  * 加密,key可以是公钥，也可以是私钥
	  *
	  * @param message
	  * @return
	  * @throws Exception
	  */
	 public byte[] encrypt(String message, Key key) throws Exception {
	  Cipher cipher = Cipher.getInstance("RSA");
	  cipher.init(Cipher.ENCRYPT_MODE, key);
	  return cipher.doFinal(message.getBytes());
	 }
	 /**
	  * 解密，key可以是公钥，也可以是私钥，如果是公钥加密就用私钥解密，反之亦然
	  *
	  * @param message
	  * @return
	  * @throws Exception
	  */
	 public byte[] decrypt(String message, Key key) throws Exception {
	  Cipher cipher = Cipher.getInstance("RSA");
	  cipher.init(Cipher.DECRYPT_MODE, key);
	  return cipher.doFinal(toBytes(message));
	 }
	 /**
	  * 用私钥签名
	  *
	  * @param message
	  * @param key
	  * @return
	  * @throws Exception
	  */
	 public byte[] sign(String message, PrivateKey key) throws Exception {
	  Signature signetcheck = Signature.getInstance("MD5withRSA");
	  signetcheck.initSign(key);
	  signetcheck.update(message.getBytes("ISO-8859-1"));
	  return signetcheck.sign();
	 }
	 /**
	  * 用公钥验证签名的正确性
	  *
	  * @param message
	  * @param signStr
	  * @return
	  * @throws Exception
	  */
	 public boolean verifySign(String message, String signStr, PublicKey key)
	   throws Exception {
	  if (message == null || signStr == null || key == null) {
	   return false;
	  }
	  Signature signetcheck = Signature.getInstance("MD5withRSA");
	  signetcheck.initVerify(key);
	  signetcheck.update(message.getBytes("ISO-8859-1"));
	  return signetcheck.verify(toBytes(signStr));
	 }

	 /**
	  * 从文件读取object
	  *
	  * @param fileName
	  * @return
	  * @throws Exception
	  */
	 private Object readFromFile(String fileName) throws Exception {
	  ObjectInputStream input = new ObjectInputStream(new FileInputStream(
	    fileName));
	  Object obj = input.readObject();
	  input.close();
	  return obj;
	 }

	 public static String toHexString(byte[] b) {
	  StringBuilder sb = new StringBuilder(b.length * 2);
	  for (int i = 0; i < b.length; i++) {
	   sb.append(HEXCHAR[(b[i] & 0xf0) >>> 4]);
	   sb.append(HEXCHAR[b[i] & 0x0f]);
	  }
	  return sb.toString();
	 }

	 public static final byte[] toBytes(String s) {
	  byte[] bytes;
	  bytes = new byte[s.length() / 2];
	  for (int i = 0; i < bytes.length; i++) {
	   bytes[i] = (byte) Integer.parseInt(s.substring(2 * i, 2 * i + 2),
	     16);
	  }
	  return bytes;
	 }

	 private static char[] HEXCHAR = { '0', '1', '2', '3', '4', '5', '6', '7',
	   '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
}