RSA加密及在Android中的使用

RSA加密及在Android中的使用"/>

RSA加密及在Android中的使用

1. RSA简介

RSA是一种常用的非对称加密算法，所谓非对称加密是指使用一对密钥（公钥和私钥）进行加密和解密，公钥人人都可以获得，用于加密数据，私钥保存在服务器中，用于解密数据。加密解密过程如下：

使用RSA进行加密解密，其优点是非常不容易破解，缺点是和对称加密（如AES）相比，加密速度较慢。因此，实际使用中，常常将对称加密和非对称加密结合使用，即使用非对称加密协商对称加密的密钥，使用对称加密密钥加密传输内容。

2. 在Android中使用RSA

Java中已内置RSA支持，示例代码如下：

2.1 生成随机公钥私钥

随机生成公钥和私钥，用于测试RSA加密解密

    /*** 私钥*/private static RSAPrivateKey privateKey;/*** 公钥*/private static RSAPublicKey publicKey;/*** 随机生成密钥对*/public static void genKeyPair() {KeyPairGenerator keyPairGen = null;try {keyPairGen = KeyPairGenerator.getInstance("RSA");} catch (NoSuchAlgorithmException e) {e.printStackTrace();}keyPairGen.initialize(1024, new SecureRandom());KeyPair keyPair = keyPairGen.generateKeyPair();privateKey = (RSAPrivateKey) keyPair.getPrivate();publicKey = (RSAPublicKey) keyPair.getPublic();}

2.2 加载公钥/私钥

从字符串/文件输入流中加载公钥

    /*** 从字符串中加载公钥** @param publicKeyStr 公钥数据字符串* @throws Exception 加载公钥时产生的异常*/public static void loadPublicKey(String publicKeyStr) throws Exception {try {byte[] buffer = EnDecryptionUtil.base64Decode(publicKeyStr);KeyFactory keyFactory = KeyFactory.getInstance("RSA");X509EncodedKeySpec keySpec = new X509EncodedKeySpec(buffer);publicKey = (RSAPublicKey) keyFactory.generatePublic(keySpec);} catch (NoSuchAlgorithmException e) {throw new Exception("无此算法");} catch (InvalidKeySpecException e) {throw new Exception("公钥非法");} catch (NullPointerException e) {throw new Exception("公钥数据为空");}}/*** 从文件输入流中加载公钥** @param in 公钥输入流* @throws Exception 加载公钥时产生的异常*/public static void loadPublicKey(InputStream in) throws Exception {try {BufferedReader br = new BufferedReader(new InputStreamReader(in));String readLine = null;StringBuilder sb = new StringBuilder();while ((readLine = br.readLine()) != null) {if (readLine.charAt(0) == '-') {continue;} else {sb.append(readLine);sb.append('\r');}}loadPublicKey(sb.toString());} catch (IOException e) {throw new Exception("公钥数据流读取错误");} catch (NullPointerException e) {throw new Exception("公钥输入流为空");}}

从字符串/文件输入流中加载私钥

    /*** 从字符串中加载私钥* @param privateKeyStr* @throws Exception*/public static void loadPrivateKey(String privateKeyStr) throws Exception {try {byte[] buffer = EnDecryptionUtil.base64Decode(privateKeyStr);PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(buffer);KeyFactory keyFactory = KeyFactory.getInstance("RSA");privateKey = (RSAPrivateKey) keyFactory.generatePrivate(keySpec);} catch (NoSuchAlgorithmException e) {throw new Exception("无此算法");} catch (InvalidKeySpecException e) {throw new Exception("私钥非法");} catch (NullPointerException e) {throw new Exception("私钥数据为空");}}/*** 从文件输入流中加载私钥** @param in 私钥输入流* @return 是否成功* @throws Exception*/public static void loadPrivateKey(InputStream in) throws Exception {try {BufferedReader br = new BufferedReader(new InputStreamReader(in));String readLine = null;StringBuilder sb = new StringBuilder();while ((readLine = br.readLine()) != null) {if (readLine.charAt(0) == '-') {continue;} else {sb.append(readLine);sb.append('\r');}}loadPrivateKey(sb.toString());} catch (IOException e) {throw new Exception("私钥数据读取错误");} catch (NullPointerException e) {throw new Exception("私钥输入流为空");}}

2.3 RSA加密数据

    /*** RSA加密过程** @param publicKey     公钥* @param plainTextData 明文数据* @return 密文数据* @throws Exception 加密过程中的异常信息*/public static byte[] encrypt(RSAPublicKey publicKey, byte[] plainTextData) throws Exception {if (publicKey == null) {throw new Exception("加密公钥为空, 请设置");}Cipher cipher;try {cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");cipher.init(Cipher.ENCRYPT_MODE, publicKey);return cipher.doFinal(plainTextData);} catch (NoSuchAlgorithmException e) {throw new Exception("无此加密算法");} catch (NoSuchPaddingException e) {e.printStackTrace();return null;} catch (InvalidKeyException e) {throw new Exception("加密公钥非法,请检查");} catch (IllegalBlockSizeException e) {throw new Exception("明文长度非法");} catch (BadPaddingException e) {throw new Exception("明文数据已损坏");}}

加密后获得的byte[]数组一般会进行Base64编码

2.4 RSA解密

    /*** RSA解密** @param privateKey 私钥* @param cipherData 密文数据* @return 明文数据* @throws Exception 解密过程中的异常信息*/public static byte[] decrypt(RSAPrivateKey privateKey, byte[] cipherData) throws Exception {if (privateKey == null) {throw new Exception("解密私钥为空, 请设置");}Cipher cipher = null;try {cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");cipher.init(Cipher.DECRYPT_MODE, privateKey);return cipher.doFinal(cipherData);} catch (NoSuchAlgorithmException e) {throw new Exception("无此解密算法");} catch (NoSuchPaddingException e) {e.printStackTrace();return null;} catch (InvalidKeyException e) {throw new Exception("解密私钥非法,请检查");} catch (IllegalBlockSizeException e) {throw new Exception("密文长度非法");} catch (BadPaddingException e) {throw new Exception("密文数据已损坏");}}

如果输入的密文进行过Base64编码，需Base64解码后再进行RSA解密

3 示例代码调用结果

公钥:
-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDO2TVhB1VIpUhNb5+owamkjmU8dNEMJyTbakBT
b7GysKaA+byMRqJLRAbVPj+eD15erREOkv9A1z4mOMo7i+7hb6J8LuktCDWC5QeusvbwlpOjjIE6
Sq8pETHPnHX5dd+ORFYWPrbd7drSIv0Fbm3R7zi0LhuJn3JWkLf1JEFDywIDAQAB
-----END PUBLIC KEY-----
私钥:
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----待加密明文:123456
加密后Base64数据:KMzWgXeWLpc31/D3LOv65AYquARkNCoPNVy+vqZd4ASC8hev1iZtBOowmWp5mMr0pYHya9AK6AngGZmT2KzS472r+UR6LJxY7u3qthGuWiWcWmZbyH/z2LEB6du60b8BOpa670GE/HB074z85kPTWCWE3kvBNDbYvDdfjMD/8JY=待解密Base64密文:KMzWgXeWLpc31/D3LOv65AYquARkNCoPNVy+vqZd4ASC8hev1iZtBOowmWp5mMr0pYHya9AK6AngGZmT2KzS472r+UR6LJxY7u3qthGuWiWcWmZbyH/z2LEB6du60b8BOpa670GE/HB074z85kPTWCWE3kvBNDbYvDdfjMD/8JY=
解密后数据:123456

每次加密后输出加密结果不同，可在在线RSA加密解密中验证