Decryption error: blocking block is damaged

Question

I have the following code.

    byte[] input = etInput.getText().toString().getBytes();
    byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
        0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 };

    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);

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

    String strLength = new String(cipherText,"US-ASCII");
    byte[] byteCiphterText = strLength.getBytes("US-ASCII");
    Log.e("Decrypt", Integer.toString(byteCiphterText.length));

    etOutput.setText(new String(cipherText,"US-ASCII"));

    cipherText  = etOutput.getText().toString().getBytes("US-ASCII");
    Log.e("Decrypt", Integer.toString(cipherText.length));

    ptLength += cipher.doFinal(plainText, ptLength);
    Log.e("Decrypt", new String(plainText));
    Log.e("Decrypt", Integer.toString(ptLength));

It works great. But as soon as I transform it into a class. It always gets the error on this line.

 ptLength += cipher.doFinal(plainText, ptLength);

 Error:Pad block corrupted

I checked and both codes are exactly the same. Even the value passed in the conversion string to a byte number is no different from the code above. Any idea what is wrong with the code?

public String Encrypt(String strPlainText) throws Exception, NoSuchProviderException,
        NoSuchPaddingException {
    byte[] input = strPlainText.getBytes();
    byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05,
            0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
            0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 };

    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);

    return new String(cipherText, "US-ASCII");
}

public String Decrypt(String strCipherText) throws Exception,
        NoSuchProviderException, NoSuchPaddingException {
    byte[] cipherText = strCipherText.getBytes("US-ASCII");
    int ctLength = cipherText.length;
    byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05,
            0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
            0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 };

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

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

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

    return new String(plainText);
}

Answer 1

As Yann Ramin said, using String is an in / out encryption failure. This is binary data that

• may contain 0x00
• may contain values ​​that are not defined or mapped to strange places in the encoding used.

[], , base64 [].

// this is a quick example - dont use sun.misc inproduction
//  - go for some open source implementation
String encryptedString = new sun.misc.BASE64Encoder.encodeBuffer(encryptedBytes);

.

, - (IMHO):

static public byte[] decrypt(Cipher cipher, SecretKey key, byte[]... bytes)
        throws GeneralSecurityException, IOException {
    cipher.init(Cipher.DECRYPT_MODE, key);
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    for (int i = 0; i < bytes.length; i++) {
        bos.write(cipher.update(bytes[i]));
    }
    bos.write(cipher.doFinal());
    return bos.toByteArray();
}

Answer 2

PKCS7 Padding. String? 1:1 , ? String , .

Answer 3

, , , , / ( ). , 500 , - 16 , 512 (32 ) - 12 .

, , , . , .