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Java RSA加密解密實現方法分析【附BASE64 jar包下載】

發布時間：2020-10-20 14:19:06 來源：腳本之家 閱讀：230 作者：Central-Perk 欄目：編程語言

本文實例講述了Java RSA加密解密實現方法。分享給大家供大家參考，具體如下：

該工具類中用到了BASE64，需要借助第三方類庫：javabase64-1.3.1.jar

javabase64-1.3.1.jar 本站下載地址。

注意：

RSA加密明文最大長度117字節，解密要求密文最大長度為128字節，所以在加密和解密的過程中需要分塊進行。

RSA加密對明文的長度是有限制的，如果加密數據過大會拋出如下異常：

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公鑰/私鑰/簽名工具包
 * </p>
 * <p>
 * 羅納德·李維斯特（Ron [R]ivest）、阿迪·薩莫爾（Adi [S]hamir）和倫納德·阿德曼（Leonard [A]dleman）
 * </p>
 * <p>
 * 字符串格式的密鑰在未在特殊說明情況下都為BASE64編碼格式<br/>
 * 由于非對稱加密速度極其緩慢，一般文件不使用它來加密而是使用對稱加密，<br/>
 * 非對稱加密算法可以用來對對稱加密的密鑰加密，這樣保證密鑰的安全也就保證了數據的安全
 * </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";
 /** *//**
 * 簽名算法
 */
 public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
 /** *//**
 * 獲取公鑰的key
 */
 private static final String PUBLIC_KEY = "RSAPublicKey";
 /** *//**
 * 獲取私鑰的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>
 * 生成密鑰對(公鑰和私鑰)
 * </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>
 * 用私鑰對信息生成數字簽名
 * </p>
 *
 * @param data 已加密數據
 * @param privateKey 私鑰(BASE64編碼)
 *
 * @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>
 * 校驗數字簽名
 * </p>
 *
 * @param data 已加密數據
 * @param publicKey 公鑰(BASE64編碼)
 * @param sign 數字簽名
 *
 * @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>
 * 私鑰解密
 * </p>
 *
 * @param encryptedData 已加密數據
 * @param privateKey 私鑰(BASE64編碼)
 * @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;
 // 對數據分段解密
 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>
 * 公鑰解密
 * </p>
 *
 * @param encryptedData 已加密數據
 * @param publicKey 公鑰(BASE64編碼)
 * @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;
 // 對數據分段解密
 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>
 * 公鑰加密
 * </p>
 *
 * @param data 源數據
 * @param publicKey 公鑰(BASE64編碼)
 * @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);
 // 對數據加密
 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;
 // 對數據分段加密
 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>
 * 私鑰加密
 * </p>
 *
 * @param data 源數據
 * @param privateKey 私鑰(BASE64編碼)
 * @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;
 // 對數據分段加密
 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>
 * 獲取私鑰
 * </p>
 *
 * @param keyMap 密鑰對
 * @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>
 * 獲取公鑰
 * </p>
 *
 * @param keyMap 密鑰對
 * @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編碼解碼工具包
 * </p>
 * <p>
 * 依賴javabase64-1.3.1.jar
 * </p>
 *
 * @author IceWee
 * @date 2012-5-19
 * @version 1.0
 */
public class Base64Utils {
 /** *//**
 * 文件讀取緩沖區大小
 */
 private static final int CACHE_SIZE = 1024;
 /** *//**
 * <p>
 * BASE64字符串解碼為二進制數據
 * </p>
 *
 * @param base64
 * @return
 * @throws Exception
 */
 public static byte[] decode(String base64) throws Exception {
 return Base64.decode(base64.getBytes());
 }
 /** *//**
 * <p>
 * 二進制數據編碼為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>
 * 將文件編碼為BASE64字符串
 * </p>
 * <p>
 * 大文件慎用，可能會導致內存溢出
 * </p>
 *
 * @param filePath 文件絕對路徑
 * @return
 * @throws Exception
 */
 public static String encodeFile(String filePath) throws Exception {
 byte[] bytes = fileToByte(filePath);
 return encode(bytes);
 }
 /** *//**
 * <p>
 * BASE64字符串轉回文件
 * </p>
 *
 * @param filePath 文件絕對路徑
 * @param base64 編碼字符串
 * @throws Exception
 */
 public static void decodeToFile(String filePath, String base64) throws Exception {
 byte[] bytes = decode(base64);
 byteArrayToFile(bytes, filePath);
 }
 /** *//**
 * <p>
 * 文件轉換為二進制數組
 * </p>
 *
 * @param filePath 文件路徑
 * @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>
 * 二進制數據寫文件
 * </p>
 *
 * @param bytes 二進制數據
 * @param filePath 文件生成目錄
 */
 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("公鑰: \n\r" + publicKey);
  System.err.println("私鑰： \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("公鑰加密——私鑰解密");
 String source = "這是一行沒有任何意義的文字，你看完了等于沒看，不是嗎？";
 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("私鑰加密——公鑰解密");
 String source = "這是一行測試RSA數字簽名的無意義文字";
 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("私鑰簽名——公鑰驗證簽名");
 String sign = RSAUtils.sign(encodedData, privateKey);
 System.err.println("簽名:\r" + sign);
 boolean status = RSAUtils.verify(encodedData, publicKey, sign);
 System.err.println("驗證結果:\r" + status);
 }
}

PS：關于加密解密感興趣的朋友還可以參考本站在線工具：

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

MD5在線加密工具:
http://tools.jb51.net/password/CreateMD5Password

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

在線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

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

更多關于java相關內容感興趣的讀者可查看本站專題：《Java數學運算技巧總結》、《Java數據結構與算法教程》、《Java字符與字符串操作技巧總結》、《Java操作DOM節點技巧總結》和《Java緩存操作技巧匯總》

希望本文所述對大家java程序設計有所幫助。

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