Java中的RSA加密解密实现

该工具类中用到了BASE64，需要借助第三方类库：javabase64-1.3.1.jar

下载地址：http://download.csdn.net/detail/centralperk/5025595

注意：
RSA加密明文最大长度117字节，解密要求密文最大长度为128字节，所以在加密和解密的过程中需要分块进行。
RSA加密对明文的长度是有限制的，如果加密数据过大会抛出如下异常：

 Exception in thread "main" javax.crypto.IllegalBlockSizeException: Data must not be longer than 117 bytes
     at com.sun.crypto.provider.RSACipher.a(DashoA13*..)
     at com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..)
     at javax.crypto.Cipher.doFinal(DashoA13*..)

RSAUtils.java

 package security;

 import java.io.ByteArrayOutputStream;
 import java.security.Key;
 import java.security.KeyFactory;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
 import java.security.PrivateKey;
 import java.security.PublicKey;
 import java.security.Signature;
 import java.security.interfaces.RSAPrivateKey;
 import java.security.interfaces.RSAPublicKey;
 import java.security.spec.PKCS8EncodedKeySpec;
 import java.security.spec.X509EncodedKeySpec;
 import java.util.HashMap;
 import java.util.Map;

 import javax.crypto.Cipher;

 /** *//**
  * <p>
  * RSA公钥/私钥/签名工具包
  * </p>
  * <p>
  * 罗纳德·李维斯特（Ron [R]ivest）、阿迪·萨莫尔（Adi [S]hamir）和伦纳德·阿德曼（Leonard [A]dleman）
  * </p>
  * <p>
  * 字符串格式的密钥在未在特殊说明情况下都为BASE64编码格式<br/>
  * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/>
  * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
  * </p>
  *
  * @author IceWee
  * @date 2012-4-26
  * @version 1.0
  */
 public class RSAUtils {

     /** *//**
      * 加密算法RSA
      */
     public static final String KEY_ALGORITHM = "RSA";

     /** *//**
      * 签名算法
      */
     public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

     /** *//**
      * 获取公钥的key
      */
     private static final String PUBLIC_KEY = "RSAPublicKey";

     /** *//**
      * 获取私钥的key
      */
     private static final String PRIVATE_KEY = "RSAPrivateKey";

     /** *//**
      * RSA最大加密明文大小
      */
     private static final int MAX_ENCRYPT_BLOCK = 117;

     /** *//**
      * RSA最大解密密文大小
      */
     private static final int MAX_DECRYPT_BLOCK = 128;

     /** *//**
      * <p>
      * 生成密钥对(公钥和私钥)
      * </p>
      *
      * @return
      * @throws Exception
      */
     public static Map<String, Object> genKeyPair() throws Exception {
         KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
         keyPairGen.initialize(1024);
         KeyPair keyPair = keyPairGen.generateKeyPair();
         RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
         RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
         Map<String, Object> keyMap = new HashMap<String, Object>(2);
         keyMap.put(PUBLIC_KEY, publicKey);
         keyMap.put(PRIVATE_KEY, privateKey);
         return keyMap;
     }

     /** *//**
      * <p>
      * 用私钥对信息生成数字签名
      * </p>
      *
      * @param data 已加密数据
      * @param privateKey 私钥(BASE64编码)
      *
      * @return
      * @throws Exception
      */
     public static String sign(byte[] data, String privateKey) throws Exception {
         byte[] keyBytes = Base64Utils.decode(privateKey);
         PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
         PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
         Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
         signature.initSign(privateK);
         signature.update(data);
         return Base64Utils.encode(signature.sign());
     }

     /** *//**
      * <p>
      * 校验数字签名
      * </p>
      *
      * @param data 已加密数据
      * @param publicKey 公钥(BASE64编码)
      * @param sign 数字签名
      *
      * @return
      * @throws Exception
      *
      */
     public static boolean verify(byte[] data, String publicKey, String sign)
             throws Exception {
         byte[] keyBytes = Base64Utils.decode(publicKey);
         X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
         PublicKey publicK = keyFactory.generatePublic(keySpec);
         Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
         signature.initVerify(publicK);
         signature.update(data);
         return signature.verify(Base64Utils.decode(sign));
     }

     /** *//**
      * <P>
      * 私钥解密
      * </p>
      *
      * @param encryptedData 已加密数据
      * @param privateKey 私钥(BASE64编码)
      * @return
      * @throws Exception
      */
     public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
             throws Exception {
         byte[] keyBytes = Base64Utils.decode(privateKey);
         PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
         Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
         cipher.init(Cipher.DECRYPT_MODE, privateK);
         int inputLen = encryptedData.length;
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         int offSet = 0;
         byte[] cache;
         int i = 0;
         // 对数据分段解密
         while (inputLen - offSet > 0) {
             if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                 cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
             } else {
                 cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
             }
             out.write(cache, 0, cache.length);
             i++;
             offSet = i * MAX_DECRYPT_BLOCK;
         }
         byte[] decryptedData = out.toByteArray();
         out.close();
         return decryptedData;
     }

     /** *//**
      * <p>
      * 公钥解密
      * </p>
      *
      * @param encryptedData 已加密数据
      * @param publicKey 公钥(BASE64编码)
      * @return
      * @throws Exception
      */
     public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
             throws Exception {
         byte[] keyBytes = Base64Utils.decode(publicKey);
         X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
         Key publicK = keyFactory.generatePublic(x509KeySpec);
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
         cipher.init(Cipher.DECRYPT_MODE, publicK);
         int inputLen = encryptedData.length;
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         int offSet = 0;
         byte[] cache;
         int i = 0;
         // 对数据分段解密
         while (inputLen - offSet > 0) {
             if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                 cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
             } else {
                 cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
             }
             out.write(cache, 0, cache.length);
             i++;
             offSet = i * MAX_DECRYPT_BLOCK;
         }
         byte[] decryptedData = out.toByteArray();
         out.close();
         return decryptedData;
     }

     /** *//**
      * <p>
      * 公钥加密
      * </p>
      *
      * @param data 源数据
      * @param publicKey 公钥(BASE64编码)
      * @return
      * @throws Exception
      */
     public static byte[] encryptByPublicKey(byte[] data, String publicKey)
             throws Exception {
         byte[] keyBytes = Base64Utils.decode(publicKey);
         X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
         Key publicK = keyFactory.generatePublic(x509KeySpec);
         // 对数据加密
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
         cipher.init(Cipher.ENCRYPT_MODE, publicK);
         int inputLen = data.length;
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         int offSet = 0;
         byte[] cache;
         int i = 0;
         // 对数据分段加密
         while (inputLen - offSet > 0) {
             if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                 cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
             } else {
                 cache = cipher.doFinal(data, offSet, inputLen - offSet);
             }
             out.write(cache, 0, cache.length);
             i++;
             offSet = i * MAX_ENCRYPT_BLOCK;
         }
         byte[] encryptedData = out.toByteArray();
         out.close();
         return encryptedData;
     }

     /** *//**
      * <p>
      * 私钥加密
      * </p>
      *
      * @param data 源数据
      * @param privateKey 私钥(BASE64编码)
      * @return
      * @throws Exception
      */
     public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
             throws Exception {
         byte[] keyBytes = Base64Utils.decode(privateKey);
         PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
         Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
         cipher.init(Cipher.ENCRYPT_MODE, privateK);
         int inputLen = data.length;
         ByteArrayOutputStream out = new ByteArrayOutputStream();
         int offSet = 0;
         byte[] cache;
         int i = 0;
         // 对数据分段加密
         while (inputLen - offSet > 0) {
             if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                 cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
             } else {
                 cache = cipher.doFinal(data, offSet, inputLen - offSet);
             }
             out.write(cache, 0, cache.length);
             i++;
             offSet = i * MAX_ENCRYPT_BLOCK;
         }
         byte[] encryptedData = out.toByteArray();
         out.close();
         return encryptedData;
     }

     /** *//**
      * <p>
      * 获取私钥
      * </p>
      *
      * @param keyMap 密钥对
      * @return
      * @throws Exception
      */
     public static String getPrivateKey(Map<String, Object> keyMap)
             throws Exception {
         Key key = (Key) keyMap.get(PRIVATE_KEY);
         return Base64Utils.encode(key.getEncoded());
     }

     /** *//**
      * <p>
      * 获取公钥
      * </p>
      *
      * @param keyMap 密钥对
      * @return
      * @throws Exception
      */
     public static String getPublicKey(Map<String, Object> keyMap)
             throws Exception {
         Key key = (Key) keyMap.get(PUBLIC_KEY);
         return Base64Utils.encode(key.getEncoded());
     }

 }

Base64Utils.java

 package security;

 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.InputStream;
 import java.io.OutputStream;

 import it.sauronsoftware.base64.Base64;

 /** *//**
  * <p>
  * BASE64编码解码工具包
  * </p>
  * <p>
  * 依赖javabase64-1.3.1.jar
  * </p>
  *
  * @author IceWee
  * @date 2012-5-19
  * @version 1.0
  */
 public class Base64Utils {

     /** *//**
      * 文件读取缓冲区大小
      */
     private static final int CACHE_SIZE = 1024;

     /** *//**
      * <p>
      * BASE64字符串解码为二进制数据
      * </p>
      *
      * @param base64
      * @return
      * @throws Exception
      */
     public static byte[] decode(String base64) throws Exception {
         return Base64.decode(base64.getBytes());
     }

     /** *//**
      * <p>
      * 二进制数据编码为BASE64字符串
      * </p>
      *
      * @param bytes
      * @return
      * @throws Exception
      */
     public static String encode(byte[] bytes) throws Exception {
         return new String(Base64.encode(bytes));
     }

     /** *//**
      * <p>
      * 将文件编码为BASE64字符串
      * </p>
      * <p>
      * 大文件慎用，可能会导致内存溢出
      * </p>
      *
      * @param filePath 文件绝对路径
      * @return
      * @throws Exception
      */
     public static String encodeFile(String filePath) throws Exception {
         byte[] bytes = fileToByte(filePath);
         return encode(bytes);
     }

     /** *//**
      * <p>
      * BASE64字符串转回文件
      * </p>
      *
      * @param filePath 文件绝对路径
      * @param base64 编码字符串
      * @throws Exception
      */
     public static void decodeToFile(String filePath, String base64) throws Exception {
         byte[] bytes = decode(base64);
         byteArrayToFile(bytes, filePath);
     }

     /** *//**
      * <p>
      * 文件转换为二进制数组
      * </p>
      *
      * @param filePath 文件路径
      * @return
      * @throws Exception
      */
     public static byte[] fileToByte(String filePath) throws Exception {
         byte[] data = new byte[0];
         File file = new File(filePath);
         if (file.exists()) {
             FileInputStream in = new FileInputStream(file);
             ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
             byte[] cache = new byte[CACHE_SIZE];
             int nRead = 0;
             while ((nRead = in.read(cache)) != -1) {
                 out.write(cache, 0, nRead);
                 out.flush();
             }
             out.close();
             in.close();
             data = out.toByteArray();
          }
         return data;
     }

     /** *//**
      * <p>
      * 二进制数据写文件
      * </p>
      *
      * @param bytes 二进制数据
      * @param filePath 文件生成目录
      */
     public static void byteArrayToFile(byte[] bytes, String filePath) throws Exception {
         InputStream in = new ByteArrayInputStream(bytes);
         File destFile = new File(filePath);
         if (!destFile.getParentFile().exists()) {
             destFile.getParentFile().mkdirs();
         }
         destFile.createNewFile();
         OutputStream out = new FileOutputStream(destFile);
         byte[] cache = new byte[CACHE_SIZE];
         int nRead = 0;
         while ((nRead = in.read(cache)) != -1) {
             out.write(cache, 0, nRead);
             out.flush();
         }
         out.close();
         in.close();
     }


 }

 

RSATester.java

 package security;

 import java.util.Map;

 public class RSATester {

     static String publicKey;
     static String privateKey;

     static {
         try {
             Map<String, Object> keyMap = RSAUtils.genKeyPair();
             publicKey = RSAUtils.getPublicKey(keyMap);
             privateKey = RSAUtils.getPrivateKey(keyMap);
             System.err.println("公钥: \n\r" + publicKey);
             System.err.println("私钥： \n\r" + privateKey);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     public static void main(String[] args) throws Exception {
         test();
         testSign();
     }

     static void test() throws Exception {
         System.err.println("公钥加密——私钥解密");
         String source = "这是一行没有任何意义的文字，你看完了等于没看，不是吗？";
         System.out.println("\r加密前文字：\r\n" + source);
         byte[] data = source.getBytes();
         byte[] encodedData = RSAUtils.encryptByPublicKey(data, publicKey);
         System.out.println("加密后文字：\r\n" + new String(encodedData));
         byte[] decodedData = RSAUtils.decryptByPrivateKey(encodedData, privateKey);
         String target = new String(decodedData);
         System.out.println("解密后文字: \r\n" + target);
     }

     static void testSign() throws Exception {
         System.err.println("私钥加密——公钥解密");
         String source = "这是一行测试RSA数字签名的无意义文字";
         System.out.println("原文字：\r\n" + source);
         byte[] data = source.getBytes();
         byte[] encodedData = RSAUtils.encryptByPrivateKey(data, privateKey);
         System.out.println("加密后：\r\n" + new String(encodedData));
         byte[] decodedData = RSAUtils.decryptByPublicKey(encodedData, publicKey);
         String target = new String(decodedData);
         System.out.println("解密后: \r\n" + target);
         System.err.println("私钥签名——公钥验证签名");
         String sign = RSAUtils.sign(encodedData, privateKey);
         System.err.println("签名:\r" + sign);
         boolean status = RSAUtils.verify(encodedData, publicKey, sign);
         System.err.println("验证结果:\r" + status);
     }

 }