java与IOS之间的RSA加解密

    很简单的一个需求，ipad端给密码RSA加密，传到java后台，解密。RSA加密算法是基于一个密钥对的，分为公钥和私钥，一般情况公钥加密，私钥解密，但也可私钥加密，公钥解密。还可以验签，就是先用私钥对数据进行加密，然后对加密后的数据进行签名，得到一个签名值。然后再用公钥先验签，证明是对应私钥加密过的数据才解密。主要是为了防止来源不确定的数据。 
    根据上面的介绍，大家也都知道，RSA算法的关键就是密钥对，我和IOS的同事各自找了RSA的算法实现代码，都能正常根据密钥对加解密。问题是我们各自使用对方的密钥对就不能加解密成功。IOS同事也是一个新手。连RSA算法是个什么概念都没搞清楚，我也懂点IOS。所以就陪着他一起看代码，找资料。看到底什么原因引起的密钥对不能共用。后来找到下面这篇文章： 
Java中使用OpenSSL生成的RSA公私钥进行数据加解密  

原来在用mac 系统中自带的openssl生成的密钥对文件是X509编码格式的。而我们JAVA所需的私钥文件是PKCS#8编码格式的。。所以要将在mac 系统中生成的私钥文件转下码就行了。转码方式参考上面链接。附下java代码： 

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.security.InvalidKeyException;
 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.InvalidKeySpecException;
 import java.security.spec.PKCS8EncodedKeySpec;
 import java.security.spec.X509EncodedKeySpec;

 import javax.crypto.BadPaddingException;
 import javax.crypto.Cipher;
 import javax.crypto.IllegalBlockSizeException;
 import javax.crypto.NoSuchPaddingException;

 import sun.misc.BASE64Decoder;
 import sun.misc.BASE64Encoder;

 public class RSAEncrypt {
     private static final String DEFAULT_PUBLIC_KEY=
         "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQChDzcjw/rWgFwnxunbKp7/4e8w" + "\r" +
         "/UmXx2jk6qEEn69t6N2R1i/LmcyDT1xr/T2AHGOiXNQ5V8W4iCaaeNawi7aJaRht" + "\r" +
         "Vx1uOH/2U378fscEESEG8XDqll0GCfB1/TjKI2aitVSzXOtRs8kYgGU78f7VmDNg" + "\r" +
         "XIlk3gdhnzh+uoEQywIDAQAB" + "\r";

     private static final String DEFAULT_PRIVATE_KEY=
         "MIICdQIBADANBgkqhkiG9w0BAQEFAASCAl8wggJbAgEAAoGBAKEPNyPD+taAXCfG" + "\r" +
         "6dsqnv/h7zD9SZfHaOTqoQSfr23o3ZHWL8uZzINPXGv9PYAcY6Jc1DlXxbiIJpp4" + "\r" +
         "1rCLtolpGG1XHW44f/ZTfvx+xwQRIQbxcOqWXQYJ8HX9OMojZqK1VLNc61GzyRiA" + "\r" +
         "ZTvx/tWYM2BciWTeB2GfOH66gRDLAgMBAAECgYBp4qTvoJKynuT3SbDJY/XwaEtm" + "\r" +
         "u768SF9P0GlXrtwYuDWjAVue0VhBI9WxMWZTaVafkcP8hxX4QZqPh84td0zjcq3j" + "\r" +
         "DLOegAFJkIorGzq5FyK7ydBoU1TLjFV459c8dTZMTu+LgsOTD11/V/Jr4NJxIudo" + "\r" +
         "MBQ3c4cHmOoYv4uzkQJBANR+7Fc3e6oZgqTOesqPSPqljbsdF9E4x4eDFuOecCkJ" + "\r" +
         "DvVLOOoAzvtHfAiUp+H3fk4hXRpALiNBEHiIdhIuX2UCQQDCCHiPHFd4gC58yyCM" + "\r" +
         "6Leqkmoa+6YpfRb3oxykLBXcWx7DtbX+ayKy5OQmnkEG+MW8XB8wAdiUl0/tb6cQ" + "\r" +
         "FaRvAkBhvP94Hk0DMDinFVHlWYJ3xy4pongSA8vCyMj+aSGtvjzjFnZXK4gIjBjA" + "\r" +
         "2Z9ekDfIOBBawqp2DLdGuX2VXz8BAkByMuIh+KBSv76cnEDwLhfLQJlKgEnvqTvX" + "\r" +
         "TB0TUw8avlaBAXW34/5sI+NUB1hmbgyTK/T/IFcEPXpBWLGO+e3pAkAGWLpnH0Zh" + "\r" +
         "Fae7oAqkMAd3xCNY6ec180tAe57hZ6kS+SYLKwb4gGzYaCxc22vMtYksXHtUeamo" + "\r" +
         "1NMLzI2ZfUoX" + "\r";

     /**
      * 私钥
      */
     private RSAPrivateKey privateKey;

     /**
      * 公钥
      */
     private RSAPublicKey publicKey;

     /**
      * 字节数据转字符串专用集合
      */
     private static final char[] HEX_CHAR= {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};


     /**
      * 获取私钥
      * @return 当前的私钥对象
      */
     public RSAPrivateKey getPrivateKey() {
         return privateKey;
     }

     /**
      * 获取公钥
      * @return 当前的公钥对象
      */
     public RSAPublicKey getPublicKey() {
         return publicKey;
     }

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

     /**
      * 从文件中输入流中加载公钥
      * @param in 公钥输入流
      * @throws Exception 加载公钥时产生的异常
      */
     public 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 void loadPublicKey(String publicKeyStr) throws Exception{
         try {
             BASE64Decoder base64Decoder= new BASE64Decoder();
             byte[] buffer= base64Decoder.decodeBuffer(publicKeyStr);
             KeyFactory keyFactory= KeyFactory.getInstance("RSA");
             X509EncodedKeySpec keySpec= new X509EncodedKeySpec(buffer);
             this.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 (IOException e) {
             throw new Exception("公钥数据内容读取错误");
         } catch (NullPointerException e) {
             throw new Exception("公钥数据为空");
         }
     }

     /**
      * 从文件中加载私钥
      * @param keyFileName 私钥文件名
      * @return 是否成功
      * @throws Exception
      */
     public 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");
         }
     }

     public void loadPrivateKey(String privateKeyStr) throws Exception{
         try {
             BASE64Decoder base64Decoder= new BASE64Decoder();
             byte[] buffer= base64Decoder.decodeBuffer(privateKeyStr);
             PKCS8EncodedKeySpec keySpec= new PKCS8EncodedKeySpec(buffer);
             KeyFactory keyFactory= KeyFactory.getInstance("RSA");
             this.privateKey= (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
         } catch (NoSuchAlgorithmException e) {
             throw new Exception("无此算法");
         } catch (InvalidKeySpecException e) {
             e.printStackTrace();
             throw new Exception("私钥非法");
         } catch (IOException e) {
             throw new Exception("私钥数据内容读取错误");
         } catch (NullPointerException e) {
             throw new Exception("私钥数据为空");
         }
     }

     /**
      * 加密过程
      * @param publicKey 公钥
      * @param plainTextData 明文数据
      * @return
      * @throws Exception 加密过程中的异常信息
      */
     public 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= null;
         try {
             cipher= Cipher.getInstance("RSA");//, new BouncyCastleProvider());
             cipher.init(Cipher.ENCRYPT_MODE, publicKey);
             byte[] output= cipher.doFinal(plainTextData);
             return output;
         } 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");
         }
     }

     /**
      * 解密过程
      * @param privateKey 私钥
      * @param cipherData 密文数据
      * @return 明文
      * @throws Exception 解密过程中的异常信息
      */
     public 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");//, new BouncyCastleProvider());
             cipher.init(Cipher.DECRYPT_MODE, privateKey);
             byte[] output= cipher.doFinal(cipherData);
             return output;
         } 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");
         }
     }


     /**
      * 字节数据转十六进制字符串
      * @param data 输入数据
      * @return 十六进制内容
      */
     public static String byteArrayToString(byte[] data){
         StringBuilder stringBuilder= new StringBuilder();
         for (int i=0; i<data.length; i++){
             //取出字节的高四位 作为索引得到相应的十六进制标识符 注意无符号右移
             stringBuilder.append(HEX_CHAR[(data[i] & 0xf0)>>> 4]);
             //取出字节的低四位 作为索引得到相应的十六进制标识符
             stringBuilder.append(HEX_CHAR[(data[i] & 0x0f)]);
             if (i<data.length-1){
                 stringBuilder.append(' ');
             }
         }
         return stringBuilder.toString();
     }


     public static void main(String[] args){
         RSAEncrypt rsaEncrypt= new RSAEncrypt();
         //rsaEncrypt.genKeyPair();


         //加载公钥
         try {
             rsaEncrypt.loadPublicKey(RSAEncrypt.DEFAULT_PUBLIC_KEY);
             System.out.println("加载公钥成功");
         } catch (Exception e) {
             System.err.println(e.getMessage());
             System.err.println("加载公钥失败");
         }

         //加载私钥
         try {
             rsaEncrypt.loadPrivateKey(RSAEncrypt.DEFAULT_PRIVATE_KEY);
             System.out.println("加载私钥成功");
         } catch (Exception e) {
             System.err.println(e.getMessage());
             System.err.println("加载私钥失败");
         }

         //测试字符串
         String encryptStr= "abc";
         System.out.println("私钥长度："+rsaEncrypt.getPrivateKey().toString().length());
         System.out.println("公钥长度："+rsaEncrypt.getPublicKey().toString().length());
         try {
             //加密
             byte[] cipher = rsaEncrypt.encrypt(rsaEncrypt.getPublicKey(), encryptStr.getBytes());


             //解密
             byte[] plainText = rsaEncrypt.decrypt(rsaEncrypt.getPrivateKey(), cipher);



             System.out.println("密文长度:"+ cipher.length);
             System.out.println(RSAEncrypt.byteArrayToString(cipher));
             System.out.println("明文长度:"+ plainText.length);
             System.out.println(RSAEncrypt.byteArrayToString(plainText));
             System.out.println(new String(plainText));
         } catch (Exception e) {
             System.err.println(e.getMessage());
         }
     }
 }

提供两种方式加载密钥对，可通过字符串或者文件流，文件是指生成的.pem文件才可以哦。 
另外附一份IOS中加密方法，不过这里要求的文件是der。 
http://blog.yorkgu.me/2011/10/27/rsa-in-ios-using-publick-key-generated-by-openssl/  IOS中加密后返回的NSdata对象，可以对NSdata对象进行base64编码转换成字符串，然后java用BASE64Decoder解码之后，就转换成了byte[]，可直接用上面方法解密。。。