增加RSA加密解密工具类和相关jar
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zengfantian
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package com.zftlive.android.library.tools.security;
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import org.bouncycastle.jce.provider.BouncyCastleProvider;
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import java.io.ByteArrayOutputStream;
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import java.math.BigInteger;
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import java.security.Key;
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import java.security.KeyFactory;
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import java.security.KeyPair;
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import java.security.KeyPairGenerator;
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import java.security.NoSuchAlgorithmException;
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import java.security.SecureRandom;
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import java.security.interfaces.RSAPrivateKey;
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import java.security.interfaces.RSAPublicKey;
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import java.security.spec.InvalidKeySpecException;
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import java.security.spec.RSAPrivateKeySpec;
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import java.security.spec.RSAPublicKeySpec;
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import javax.crypto.Cipher;
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/**
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* RSA加密解密工具类<br>
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* RSA加密速度比DES慢很多，适合少量数据加密，生成秘钥对需要引入开源加解密方案bouncycastle，不能使用默认缺省的实现获取秘钥对，Android
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* 、Windows不同平台默认算法不一样（DES/RSA都一样，MD5都一样）<br>
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*
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* 目前被破解的最长RSA密钥是768个二进制位，RSA密钥一般是1024位，重要场合则为2048位，密钥长度越大加密越慢越安全，也容易OOM RSA
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* 工具类。提供加密，解密，生成密钥对等方法。 需要到http://www.bouncycastle.org下载bcprov-jdk14-123.jar。
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* RSA加密原理概述 RSA的安全性依赖于大数的分解，公钥和私钥都是两个大素数（大于100的十进制位）的函数。
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* 据猜测，从一个密钥和密文推断出明文的难度等同于分解两个大素数的积<br>
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* ===================================================================<br>
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* （该算法的安全性未得到理论的证明）<br>
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* =================================================================== <br>
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* 密钥的产生：<br>
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* 1.选择两个大素数 p,q ,计算 n=p*q; <br>
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* 2.随机选择加密密钥 e ,要求 e 和 (p-1)*(q-1)互质 <br>
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* 3.利用 Euclid算法计算解密密钥 d , 使其满足 e*d = 1(mod(p-1)*(q-1)) (其中 n,d 也要互质) <br>
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* 4:至此得出公钥为 (n,e)私钥为(n,d) <br>
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* ===================================================================<br>
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* 加解密方法：<br>
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* 1.首先将要加密的信息 m(二进制表示) 分成等长的数据块 m1,m <br>
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* 2,...,mi 块长 s(尽可能大) ,其中2^s<n2:对应的密文是： ci = mi^e(mod n) <br>
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* 3:解密时作如下计算： mi = ci^d(mod n)<br>
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* =================================================================== <br>
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* RSA速度
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* 由于进行的都是大数计算，使得RSA最快的情况也比DES慢上100倍，无论 是软件还是硬件实现。 速度一直是RSA的缺陷。一般来说只用于少量数据 加密。 <br>
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* 参考文献：<br>
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* http://repo1.maven.org/maven2/org/bouncycastle/
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* http://www.ruanyifeng.com/blog/2013/06/rsa_algorithm_part_one.html<br>
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* http://blog.csdn.net/yanzi1225627/article/details/26508035<br>
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* http://blog.csdn.net/bbld_/article/details/38777491<br>
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*
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* @author 曾繁添
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* @version 1.0
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*/
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public class RSA {
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/**
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* 生成密钥对（公钥和私钥）
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*
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* @param mKeySize 密钥长度,默认1024
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* @return KeyPair 密钥对，包含公钥和私钥
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* @throws Exception 生成秘钥对异常
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*/
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public static KeyPair genKeyPair(int mKeySize) throws Exception {
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KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA", new BouncyCastleProvider());
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kpg.initialize(mKeySize, new SecureRandom());
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return kpg.genKeyPair();
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}
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public void testRSA() {
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try {
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String str = "yanzi1225627";
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RSAPublicKey pubKey = getRSAPublicKey();
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RSAPrivateKey priKey = getRSAPrivateKey();
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byte[] enRsaBytes = encrypt(pubKey, str.getBytes());
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String enRsaStr = new String(enRsaBytes, "UTF-8");
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System.out.println("加密后==" + enRsaStr);
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System.out.println("解密后=="+ new String(decrypt(priKey, encrypt(pubKey, str.getBytes()))));
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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// 密钥对
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private KeyPair keyPair = null;
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/**
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* 初始化密钥对
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*/
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public void init() {
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try {
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this.keyPair = this.generateKeyPair();
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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/**
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* 生成密钥对
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*
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* @return KeyPair
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* @throws Exception
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*/
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private KeyPair generateKeyPair() throws Exception {
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try {
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KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",
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new BouncyCastleProvider());
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// 这个值关系到块加密的大小，可以更改，但是不要太大，否则效率会低
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final int KEY_SIZE = 1024;
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keyPairGen.initialize(KEY_SIZE, new SecureRandom());
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KeyPair keyPair = keyPairGen.genKeyPair();
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return keyPair;
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} catch (Exception e) {
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throw new Exception(e.getMessage());
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}
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}
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/**
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* 生成公钥
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*
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* @param modulus
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* @param publicExponent
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* @return RSAPublicKey
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* @throws Exception
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*/
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private RSAPublicKey generateRSAPublicKey(byte[] modulus, byte[] publicExponent)
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throws Exception {
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KeyFactory keyFac = null;
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try {
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keyFac = KeyFactory.getInstance("RSA", new BouncyCastleProvider());
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} catch (NoSuchAlgorithmException ex) {
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throw new Exception(ex.getMessage());
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}
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RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger(
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publicExponent));
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try {
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return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
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} catch (InvalidKeySpecException ex) {
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throw new Exception(ex.getMessage());
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}
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}
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/**
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* 生成私钥
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*
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* @param modulus
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* @param privateExponent
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* @return RSAPrivateKey
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* @throws Exception
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*/
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private RSAPrivateKey generateRSAPrivateKey(byte[] modulus, byte[] privateExponent)
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throws Exception {
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KeyFactory keyFac = null;
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try {
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keyFac = KeyFactory.getInstance("RSA", new BouncyCastleProvider());
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} catch (NoSuchAlgorithmException ex) {
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throw new Exception(ex.getMessage());
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}
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RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus),
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new BigInteger(privateExponent));
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try {
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return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
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} catch (InvalidKeySpecException ex) {
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throw new Exception(ex.getMessage());
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}
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}
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/**
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* 返回公钥
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*
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* @return
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* @throws Exception
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*/
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public RSAPublicKey getRSAPublicKey() throws Exception {
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// 获取公钥
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RSAPublicKey pubKey = (RSAPublicKey) keyPair.getPublic();
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// 获取公钥系数(字节数组形式)
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byte[] pubModBytes = pubKey.getModulus().toByteArray();
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// 返回公钥公用指数(字节数组形式)
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byte[] pubPubExpBytes = pubKey.getPublicExponent().toByteArray();
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// 生成公钥
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RSAPublicKey recoveryPubKey = this.generateRSAPublicKey(pubModBytes, pubPubExpBytes);
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return recoveryPubKey;
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}
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/**
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* 获取私钥
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*
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* @return
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* @throws Exception
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*/
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public RSAPrivateKey getRSAPrivateKey() throws Exception {
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// 获取私钥
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RSAPrivateKey priKey = (RSAPrivateKey) keyPair.getPrivate();
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// 返回私钥系数(字节数组形式)
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byte[] priModBytes = priKey.getModulus().toByteArray();
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// 返回私钥专用指数(字节数组形式)
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byte[] priPriExpBytes = priKey.getPrivateExponent().toByteArray();
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// 生成私钥
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RSAPrivateKey recoveryPriKey = this.generateRSAPrivateKey(priModBytes, priPriExpBytes);
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return recoveryPriKey;
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}
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/**
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* 加密
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*
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* @param key 加密的密钥
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* @param data 待加密的明文数据
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* @return 加密后的数据
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* @throws Exception
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*/
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public byte[] encrypt(Key key, byte[] data) throws Exception {
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try {
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Cipher cipher = Cipher.getInstance("RSA", new BouncyCastleProvider());
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cipher.init(Cipher.ENCRYPT_MODE, key);
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// 获得加密块大小，如:加密前数据为128个byte，而key_size=1024 加密块大小为127
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// byte,加密后为128个byte;
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// 因此共有2个加密块，第一个127 byte第二个为1个byte
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int blockSize = cipher.getBlockSize();
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int outputSize = cipher.getOutputSize(data.length);// 获得加密块加密后块大小
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int leavedSize = data.length % blockSize;
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int blocksSize = leavedSize != 0 ? data.length / blockSize + 1 : data.length
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/ blockSize;
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byte[] raw = new byte[outputSize * blocksSize];
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int i = 0;
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while (data.length - i * blockSize > 0) {
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if (data.length - i * blockSize > blockSize)
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cipher.doFinal(data, i * blockSize, blockSize, raw, i * outputSize);
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else
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cipher.doFinal(data, i * blockSize, data.length - i * blockSize, raw, i
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* outputSize);
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// 这里面doUpdate方法不可用，查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到ByteArrayOutputStream中
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// ，而最后doFinal的时候才将所有的byte[]进行加密，可是到了此时加密块大小很可能已经超出了OutputSize所以只好用dofinal方法。
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i++;
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}
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return raw;
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} catch (Exception e) {
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throw new Exception(e.getMessage());
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}
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}
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/**
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* 解密
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*
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* @param key 解密的密钥
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* @param raw 已经加密的数据
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* @return 解密后的明文
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* @throws Exception
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*/
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public byte[] decrypt(Key key, byte[] raw) throws Exception {
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try {
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Cipher cipher = Cipher.getInstance("RSA", new BouncyCastleProvider());
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cipher.init(cipher.DECRYPT_MODE, key);
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int blockSize = cipher.getBlockSize();
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ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
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int j = 0;
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while (raw.length - j * blockSize > 0) {
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bout.write(cipher.doFinal(raw, j * blockSize, blockSize));
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j++;
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}
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return bout.toByteArray();
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} catch (Exception e) {
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throw new Exception(e.getMessage());
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}
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}
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}
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