Java RSA加密解密实现

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

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*..)

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

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();      }              }

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);      }        }