Error RijndaelManaged, “Padding is invalid and cannot be removed”

Question

I have error from CryptoStream:

Padding is invalid and cannot be removed.

Code

public MemoryStream Enc         


        

Answer 1

Use PaddingMode.Zeros to fix problem , Following code:

   public byte[] EncryptFile(Stream input, string password, string salt)
            {

                // Essentially, if you want to use RijndaelManaged as AES you need to make sure that:
                // 1.The block size is set to 128 bits
                // 2.You are not using CFB mode, or if you are the feedback size is also 128 bits

                var algorithm = new RijndaelManaged { KeySize = 256, BlockSize = 128 };
                var key = new Rfc2898DeriveBytes(password, Encoding.ASCII.GetBytes(salt));

                algorithm.Key = key.GetBytes(algorithm.KeySize / 8);
                algorithm.IV = key.GetBytes(algorithm.BlockSize / 8);
                algorithm.Padding = PaddingMode.Zeros;

                using (Stream cryptoStream = new MemoryStream())
                using (var encryptedStream = new CryptoStream(cryptoStream, algorithm.CreateEncryptor(), CryptoStreamMode.Write))
                {
                    CopyStream(input, encryptedStream);

                    return ReadToEnd(cryptoStream);
                }
            }

            public byte[] DecryptFile(Stream input, Stream output, string password, string salt)
            {
                // Essentially, if you want to use RijndaelManaged as AES you need to make sure that:
                // 1.The block size is set to 128 bits
                // 2.You are not using CFB mode, or if you are the feedback size is also 128 bits
                var algorithm = new RijndaelManaged { KeySize = 256, BlockSize = 128 };
                var key = new Rfc2898DeriveBytes(password, Encoding.ASCII.GetBytes(salt));

                algorithm.Key = key.GetBytes(algorithm.KeySize / 8);
                algorithm.IV = key.GetBytes(algorithm.BlockSize / 8);
                algorithm.Padding = PaddingMode.Zeros;

                try
                {
                    using (var decryptedStream = new CryptoStream(output, algorithm.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        CopyStream(input, decryptedStream);
                        return ReadToEnd(output);
                    }
                }
                catch (CryptographicException ex)
                {
                    throw new InvalidDataException("Please supply a correct password");
                }
                catch (Exception ex)
                {
                    throw new Exception(ex.Message);
                }
            }

I hop help you.

Answer 2

It's work

using (FileStream fs = new FileStream( absolute, FileMode.Open )) {
    // create a CryptoStream in read mode
    using (CryptoStream cryptoStream = new CryptoStream( fs, decryptor, CryptoStreamMode.Read )) {
        int readLength = ( int )fs.Length;
        byte[] buffer = new byte[readLength];
        cryptoStream.Read( buffer, 0, readLength );
        using (MemoryStream ms = new MemoryStream( buffer )) {
            BinaryFormatter bf = new BinaryFormatter( );
            settings = ( SettingsJson )bf.Deserialize( ms );// Deserialize SettingsJson array
        }
    }
    fs.Close( );
}

Answer 3

My problem was I was taking the encryped output in bytes and converting it to a string. The string back to byte array (for decrypting) was not the same. I was using UTF8Encoding, then I tried ASCIIEnconding. Neither worked.

Convert.FromBase64String/ToBase64String worked fine, got rid of the padding issues and actually decrypted the data.

Answer 4

Please check your pass phrase - it should be same in both methods EncrypteBytes and DecrypteBytes. If both are not same, then it will generate the error.