RSA非对称加密技术（JAVA版实现加解密处理）介绍

---

      非对称的加密技术就是指加密过程是不可逆，不能通过密文直接解密得到原文信息。RSA技术就是现在比较流行的非对称的加密技术，他实现主要通过公钥加密，解密的话需要私钥进行解密。Java的加解密具体实现如下：

import java.security.Key;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.security.interfaces.RSAPrivateKey;

import java.security.interfaces.RSAPublicKey;

import java.security.spec.PKCS8EncodedKeySpec;

import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

import org.apache.commons.codec.binary.Base64;

/**

*

* RSA加密与解密工具类

*

* @author 李代锋

*

*

*/

public class RSAUtils {

/**

    * 生成密钥对

    *

    * @param keySize

    *            密钥长度

    * @return

    * @throws NoSuchAlgorithmException

*/

  public static KeyPair generateKeyPair(int keySize) {

try {

KeyPairGenerator pairgen = KeyPairGenerator.getInstance("RSA");

SecureRandom random =new SecureRandom();

//初始化密钥对生成器，密钥大小为${keySize}位

        pairgen.initialize(keySize, random);

return pairgen.generateKeyPair();

}catch (NoSuchAlgorithmException e) {

e.printStackTrace();

}

return null;

}

/**

* 将密钥采用Base64加密并返回加密后的密文

*

    * @param key

    *            密钥

    * @return

    */

  public static String keyEncrypt(Key key) {

return new String(Base64.encodeBase64(key.getEncoded()));

}

/**

    * 利用公钥进行加密

    *

    * @param str

    * @param publicKey(encodeBase64后的公钥)

    * @return

    * @throws Exception

*/

  public static String encrypt(String str, String publicKey)throws Exception {

// 对公钥进行base64编码

      byte[] decoded = Base64.decodeBase64(publicKey);

RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")

.generatePublic(new X509EncodedKeySpec(decoded));

// RSA加密

      Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.ENCRYPT_MODE, pubKey);

return Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));

}

public static String encrypt(String str,byte[] decoded)throws Exception {

// 对公钥进行base64编码

      RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")

.generatePublic(new X509EncodedKeySpec(decoded));

// RSA加密

      Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.ENCRYPT_MODE, pubKey);

return Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));

}

/**

    * 直接利用公钥加密

    *

    * @param str

    *            明文

    * @param publicKey

    *            公钥

    * @return

    * @throws Exception

*/

  public static String encrypt(String str, Key publicKey)throws Exception {

RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")

.generatePublic(new X509EncodedKeySpec(publicKey.getEncoded()));

// RSA加密

      Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.ENCRYPT_MODE, pubKey);

return Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));

}

/**

    * 利用私钥解密

    *

    * @param str

    *            加密字符串

    * @param privateKey

    *            私钥（encodeBase64后的私钥）

    * @return 明文

    * @throws Exception

    *            解密过程中的异常信息

    */

  public static String decrypt(String str, String privateKey)throws Exception {

// 64位解码加密后的字符串

      byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));

// base64编码的私钥

      byte[] decoded = Base64.decodeBase64(privateKey);

RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")

.generatePrivate(new PKCS8EncodedKeySpec(decoded));

// RSA解密

      Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.DECRYPT_MODE, priKey);

return new String(cipher.doFinal(inputByte));

}

public static String decrypt(String str,byte[] decoded)throws Exception {

// 64位解码加密后的字符串

      byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));

RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")

.generatePrivate(new PKCS8EncodedKeySpec(decoded));

// RSA解密

      Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.DECRYPT_MODE, priKey);

return new String(cipher.doFinal(inputByte));

}

/**

    * 直接利用私钥解密

    *

    * @param str

    *            密文

    * @param privateKey

    *            私钥

    * @return

    * @throws Exception

*/

  public static String decrypt(String str, Key privateKey)throws Exception {

// 64位解码加密后的字符串

      byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));

RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")

.generatePrivate(new PKCS8EncodedKeySpec(privateKey.getEncoded()));

// RSA解密

      Cipher cipher = Cipher.getInstance("RSA");

cipher.init(Cipher.DECRYPT_MODE, priKey);

return new String(cipher.doFinal(inputByte));

}

public static void main(String[] args) {

try {

String srcStr ="江山如此多娇，引无数程序员竞折腰，哈哈哈哈";

// 获取非对称密钥

        KeyPair keyPair = RSAUtils.generateKeyPair(4192);

System.out.println("公钥：" +keyEncrypt(keyPair.getPublic()));

System.out.println("☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆");

System.out.println("私钥：" +keyEncrypt(keyPair.getPrivate()));

System.out.println("☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆");

String encriptMsg = RSAUtils.encrypt(srcStr, keyPair.getPublic());

System.out.println("原始信息：" + srcStr);

System.out.println("☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆");

System.out.println("加密后的密文为："+encriptMsg);

System.out.println("☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆☆");

System.out.println("密文解密：" + RSAUtils.decrypt(encriptMsg, keyPair.getPrivate()));

}catch (Exception e) {

e.printStackTrace();

}

}

}