javax.crypto.BadPaddingException：pad塊損壞

Question

我正在嘗試加密某些東西，並對其進行解密。 我沒有解密 - 我得到了上面的例外。 我嘗試改變ctLength和ptLength，但無濟於事。 我究竟做錯了什么？
我正在嘗試加密：0 0 0 0 0 0 0 0

private Cipher encrypt(byte[] input)
{
    try
    {
        SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");

        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC");

        // encryption pass
        cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] cipherText = new byte[cipher.getOutputSize(input.length)];
        int ctLength = cipher.update(input, 0, input.length, cipherText, 0);
        ctLength += cipher.doFinal(cipherText, ctLength);
        FileOutputStream fs = new FileOutputStream(savedScoresFileName);
        fs.write(cipherText);

        return cipher;
    }
    catch (Exception e)
    {
        Log.e("encrtypt", "Exception", e);
    }

    return null;
}

private String decrypt()
{
    try
    {
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC");

        SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
        byte[] cipherText = new byte[32];

        FileInputStream fl = new FileInputStream(savedScoresFileName);
        fl.read(cipherText);

        cipher.init(Cipher.DECRYPT_MODE, key);
        byte[] plainText = new byte[cipher.getOutputSize(32)];
        int ptLength = cipher.update(cipherText, 0, 32, plainText, 0);
        ptLength += cipher.doFinal(plainText, ptLength);

        return new String(plainText).substring(0, ptLength);
    }
    catch (Exception e)
    {
        Log.e("decrypt", "Exception", e);
    }

    return null;
}

這段代碼是從這里復制過來的。

Answer 1

您的代碼存在許多問題，但您的問題是由文件讀取代碼和執行加密和解密的奇怪方法引起的。

不要使用update()方法，只需使用doFinal()並更正文件寫入/讀取代碼。 例如，您的解密方法應該類似於：

try {
  Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC");

  SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");

  // Here you need to accurately and correctly read your file into a byte
  // array. Either Google for a decent solution (there are many out there)
  // or use an existing implementation, such as Apache Commons commons-io.
  // Your existing effort is buggy and doesn't close its resources.      
  byte[] cipherText = FileUtils.readFileToByteArray(new File(savedScoresFileName));


  cipher.init(Cipher.DECRYPT_MODE, key);

  // Just one call to doFinal
  byte[] plainText = cipher.doFinal(cipherText);

  // Note: don't do this. If you create a string from a byte array,
  // PLEASE pass a charset otherwise your result is platform dependent.
  return new String(plainText);
} catch (Exception e) {
  e.printStackTrace();
}