Java RSA加密解密实现方法分析

本文实例讲述了Java RSA加密解密实现方法。分享给大家供大家参考，具体如下：

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

javabase64-1.3.1.jar 本站下载地址。

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,inputLen - offSet);
   }
   out.write(cache,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,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,MAX_ENCRYPT_BLOCK);
   } else {
    cache = cipher.doFinal(data,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,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());
 }
}

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