Java AES 給出 BadPaddingException

Question

我正在嘗試在 Java 中為我的程序編寫一個簡單的加密和解密方法。 它應該使用另一個字符串作為密鑰來加密和解密一個字符串。

在測試時，發生了BadPaddingException 。

我目前的加密方法：

public String encrypt(String strToEncrypt, String secretKey) {
        try {
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            byte[] salt = new Hash().hashString(secretKey).getBytes();
            KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt, 65536, 256);
            SecretKey tmp = factory.generateSecret(spec);
            SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            byte[] iv = cipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();
            IvParameterSpec ivspec = new IvParameterSpec(iv);
            cipher.init(Cipher.ENCRYPT_MODE, secret, ivspec);

            byte[] ciphertext = cipher.doFinal(strToEncrypt.getBytes("UTF-8"));
            System.out.println("Finished encryption");
            return new Base64().encodeToString(ciphertext);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

我目前的解密方法：

public String decrypt(String strToDecrypt, String secretKey) {  
        try {
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            byte[] salt = new Hash().hashString(secretKey).getBytes();
            KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt, 65536, 256);
            SecretKey tmp = factory.generateSecret(spec);
            SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            byte[] iv = cipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();
            IvParameterSpec ivspec = new IvParameterSpec(iv);
            cipher.init(Cipher.DECRYPT_MODE, secret, ivspec);
            
            byte[] decodedPlaintext = new Base64().decode(strToDecrypt);
            byte[] plaintext = cipher.doFinal(decodedPlaintext);
            System.out.println("Finished decryption");
            return new Base64().encodeToString(plaintext);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

我收到以下異常：

javax.crypto.BadPaddingException: Given final block not properly padded. Such issues can arise if a bad key is used during decryption.
    at java.base/com.sun.crypto.provider.CipherCore.unpad(CipherCore.java:975)
    at java.base/com.sun.crypto.provider.CipherCore.fillOutputBuffer(CipherCore.java:1056)
    at java.base/com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:853)
    at java.base/com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:446)
    at java.base/javax.crypto.Cipher.doFinal(Cipher.java:2202)

Answer 1

在 Michael 和總裁 James K. Polk 的幫助下，我可以進行加密和解密工作，並改進了鹽的生成。 我的錯誤是，我沒有使用相同的IvParameterSpec進行加密和解密。

我的加密方法：

public static String encrypt(String strToEncrypt, String secretKey) {
        try {
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            byte[] salt = new byte[16];
            SecureRandom.getInstanceStrong().nextBytes(salt);
            KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt, 65536, 256);
            SecretKey tmp = factory.generateSecret(spec);
            SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            byte[] iv = cipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();
            IvParameterSpec ivspec = new IvParameterSpec(iv);
            cipher.init(Cipher.ENCRYPT_MODE, secret, ivspec);

            byte[] ivBytes = ivspec.getIV();
            byte[] ciphertext = cipher.doFinal(strToEncrypt.getBytes("UTF-8"));
            System.out.println("Finished encryption");
            byte[] outputBytes = concat(concat(salt, ivBytes), ciphertext);
            return new Base64().encodeToString(outputBytes);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

我的解密方法：

public static String decrypt(String strToDecrypt, String secretKey) {
        try {
            byte[] decodedCiphertext = new Base64().decode(strToDecrypt);
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            byte[] salt = Arrays.copyOfRange(decodedCiphertext, 0, 16);
            KeySpec spec = new PBEKeySpec(secretKey.toCharArray(), salt, 65536, 256);
            SecretKey tmp = factory.generateSecret(spec);
            SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
            byte[] iv = Arrays.copyOfRange(decodedCiphertext, 16, 32);
            IvParameterSpec ivspec = new IvParameterSpec(iv);
            cipher.init(Cipher.DECRYPT_MODE, secret, ivspec);

            
            byte[] plaintext = cipher.doFinal(Arrays.copyOfRange(decodedCiphertext, 32, decodedCiphertext.length));
            System.out.println("Finished decryption");
            return new String(plaintext, "UTF-8");
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }