RSA算法解密 javax.crypto.BadPaddingException: Decryption error 异常

忘是亡心i 2022-12-14 03:53 131阅读 0赞

#### 背景 ####

最近需要对接京东的一个会员管家嵌入到小程序当中，在进行接口请求时，需要对敏感的字段进行RSA加密处理，所以想写一个工具类方便调用。  
生成秘钥、加密明文都没问题，就是在解密的时候时候出现了一下异常：  
![在这里插入图片描述][20201013095354468.png_pic_center]

#### 原因 ####

在使用公钥加密的时候，最后我用了Base64进行了编码

Base64.getEncoder().encodeToString(encryptedData)

而在我进行解密的时候，直接使用了字符串的getByte获取了字节数组，导致得到的字节数组无法被秘钥解密。应该先使用Base64进行解码获取字节数组，

byte[] encryptedData = Base64.getDecoder().decode(encryptedDataString);

#### 完整代码 ####

*  公共参数

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

*  生成密钥对

/** * * 生成密钥对(公钥和私钥) * * * @return * @throws Exception */
 public static Map<String, String> 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, String> keyMap = new HashMap<String, String>(2);
 keyMap.put(PUBLIC_KEY, Base64.getEncoder().encodeToString(publicKey.getEncoded()));
 keyMap.put(PRIVATE_KEY, Base64.getEncoder().encodeToString(privateKey.getEncoded()));
 return keyMap;
 }

*  公钥加密

/** * * 公钥加密 * * * @param dataBase64String 源数据 * @param publicKey 公钥(BASE64编码) * @return * @throws Exception */
 public static String encryptByPublicKey(String dataBase64String, String publicKey) throws Exception { 
 byte[] data = dataBase64String.getBytes();
 byte[] keyBytes = Base64.getDecoder().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 Base64.getEncoder().encodeToString(encryptedData);
 }

*  私钥解密

/** * * 私钥解密 * * * @param encryptedDataString 已加密数据 * @param privateKey 私钥(BASE64编码) * @return * @throws Exception */
 public static String decryptByPrivateKey(String encryptedDataString, String privateKey) throws Exception { 
 //byte[] encryptedData = encryptedDataString.getBytes();
 //应该先使用Base64方式进行解码
 byte[] encryptedData = Base64.getDecoder().decode(encryptedDataString);
 byte[] keyBytes = Base64.getDecoder().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 new String(decryptedData);
 }

*  测试代码

public static void main(String[] args) throws Exception { 
 Map<String, String> stringObjectMap = genKeyPair();
 String rsaPublicKey = stringObjectMap.get("RSAPublicKey");
 String rsaPrivateKey = stringObjectMap.get("RSAPrivateKey");
 System.out.println("公钥为：" + rsaPublicKey);
 System.out.println("私钥为：" + rsaPrivateKey);
 String text = "!1Qq@2Ww哈哈";
 
 String publicText = encryptByPublicKey(text, rsaPublicKey);
 System.out.println("公钥加密的信息为：" + publicText);
 
 String privateText = decryptByPrivateKey(publicText, rsaPrivateKey);
 System.out.println("私钥解密的信息为" + privateText);
 
 }

#### 总结 ####

其实，加密和解密都是对字节数组进行的操作，只要保证加密后的字节数组和解密前的字节数组一致就可以，以上我犯的错误就是加了一层Base64编码，但是没有使用Base64解码导致的，以后还是得更新细心鸭

[20201013095354468.png_pic_center]: /images/20221123/dddf61e23a1a424ca485a045172b583e.png