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;

public class RSAUtils {
 
 public static final String KEY_ALGORITHM = "RSA";
 
 public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
 
 private static final String PUBLIC_KEY = "RSAPublicKey";
 
 private static final String PRIVATE_KEY = "RSAPrivateKey";
 
 private static final int MAX_ENCRYPT_BLOCK = 117;
 
 private static final int MAX_DECRYPT_BLOCK = 128;
 
 public static Map 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 keyMap = new HashMap(2);
 keyMap.put(PUBLIC_KEY, publicKey);
 keyMap.put(PRIVATE_KEY, privateKey);
 return keyMap;
 }
 
 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());
 }
 
 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));
 }
 
 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;
 }
 
 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;
 }
 
 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;
 }
 
 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;
 }
 
 public static String getPrivateKey(Map keyMap)
  throws Exception {
 Key key = (Key) keyMap.get(PRIVATE_KEY);
 return base64Utils.encode(key.getEncoded());
 }
 
 public static String getPublicKey(Map 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;

public class base64Utils {
 
 private static final int CACHE_SIZE = 1024;
 
 public static byte[] decode(String base64) throws Exception {
 return base64.decode(base64.getBytes());
 }
 
 public static String encode(byte[] bytes) throws Exception {
 return new String(base64.encode(bytes));
 }
 
 public static String encodeFile(String filePath) throws Exception {
 byte[] bytes = fileToByte(filePath);
 return encode(bytes);
 }
 
 public static void decodeToFile(String filePath, String base64) throws Exception {
 byte[] bytes = decode(base64);
 byteArrayToFile(bytes, filePath);
 }
 
 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;
 }
 
 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 keyMap = RSAUtils.genKeyPair();
  publicKey = RSAUtils.getPublicKey(keyMap);
  privateKey = RSAUtils.getPrivateKey(keyMap);
  System.err.println("公钥: nr" + publicKey);
  System.err.println("私钥： nr" + 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：rn" + source);
 byte[] data = source.getBytes();
 byte[] encodedData = RSAUtils.encryptByPublicKey(data, publicKey);
 System.out.println("加密后文字：rn" + new String(encodedData));
 byte[] decodedData = RSAUtils.decryptByPrivateKey(encodedData, privateKey);
 String target = new String(decodedData);
 System.out.println("解密后文字: rn" + 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：rn" + source);
 byte[] data = source.getBytes();
 byte[] encodedData = RSAUtils.encryptByPrivateKey(data, privateKey);
 System.out.println("加密后：rn" + new String(encodedData));
 byte[] decodedData = RSAUtils.decryptByPublicKey(encodedData, publicKey);
 String target = new String(decodedData);
 System.out.println("解密后: rn" + 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);
 }
}

PS：关于加密解密感兴趣的朋友还可以参考本站在线工具：

文字在线加密解密工具（包含AES、DES、RC4等）：
http://tools.jb51.net/password/txt_encode

MD5在线加密工具:
http://tools.jb51.net/password/CreateMD5Password

在线散列/哈希算法加密工具:
http://tools.jb51.net/password/hash_encrypt

在线MD5/hash/SHA-1/SHA-2/SHA-256/SHA-512/SHA-3/RIPEMD-160加密工具：
http://tools.jb51.net/password/hash_md5_sha

在线sha1/sha224/sha256/sha384/sha512加密工具：
http://tools.jb51.net/password/sha_encode

更多关于java相关内容感兴趣的读者可查看本站专题：《Java数学运算技巧总结》、《Java数据结构与算法教程》、《Java字符与字符串操作技巧总结》、《Java操作DOM节点技巧总结》和《Java缓存操作技巧汇总》

希望本文所述对大家java程序设计有所帮助。

Java RSA加密解密实现方法分析

Java相关栏目本月热门文章