Encryption

Question

Hi there,
I have a method which gets a encrypted value and will be decrypted to a guid that I have on my database.
It almost works, but the problem is the 4 last guid characteres are missing. Why ?

public static string Decrypt<T>(string value, string password) where T : SymmetricAlgorithm, new()
        {
            byte[] vectorBytes = Encoding.ASCII.GetBytes(_vector);
            byte[] saltBytes = Encoding.ASCII.GetBytes(_salt);
            byte[] valueBytes = Convert.FromBase64String(value);

            byte[] decrypted;
            int decryptedByteCount = 0;

            using (T cipher = new T())
            {
                PasswordDeriveBytes _passwordBytes = new PasswordDeriveBytes(password, saltBytes, _hash, _iterations);
                byte[] keyBytes = _passwordBytes.GetBytes(_keySize / 8);

                cipher.Mode = CipherMode.CBC;

                try
                {
                    using (ICryptoTransform decryptor = cipher.CreateDecryptor(keyBytes, vectorBytes))
                    {
                        using (MemoryStream from = new MemoryStream(valueBytes))
                        {
                            using (CryptoStream reader = new CryptoStream(from, decryptor, CryptoStreamMode.Read))
                            {
                                decrypted = new byte[valueBytes.Length];
                                decryptedByteCount = reader.Read(decrypted, 0, decrypted.Length);
                            }
                        }
                    }
                }
                catch (Exception ex)
                {
                    return String.Empty;
                }

                cipher.Clear();
            }

            var xxxx = Encoding.UTF8.GetString(decrypted, 0, decryptedByteCount);
            return Encoding.UTF8.GetString(decrypted, 0, decryptedByteCount);
        }

Thx guys !

Answer 1

when you encrypted the data, you probably missed calling FlushFinalBlock()

Answer 2

No. I do have it.

public static string Encrypt<T>(string value, string password)
                where T : SymmetricAlgorithm, new()
        {
            byte[] vectorBytes = Encoding.ASCII.GetBytes(_vector);
            byte[] saltBytes = Encoding.ASCII.GetBytes(_salt);
            byte[] valueBytes = Encoding.UTF8.GetBytes(value);

            byte[] encrypted;
            using (T cipher = new T())
            {
                PasswordDeriveBytes _passwordBytes =
                    new PasswordDeriveBytes(password, saltBytes, _hash, _iterations);
                byte[] keyBytes = _passwordBytes.GetBytes(_keySize / 8);

                cipher.Mode = CipherMode.CBC;

                using (ICryptoTransform encryptor = cipher.CreateEncryptor(keyBytes, vectorBytes))
                {
                    using (MemoryStream to = new MemoryStream())
                    {
                        using (CryptoStream writer = new CryptoStream(to, encryptor, CryptoStreamMode.Write))
                        {
                            writer.Write(valueBytes, 0, valueBytes.Length);
                            writer.FlushFinalBlock();
                            encrypted = to.ToArray();
                        }
                    }
                }
                cipher.Clear();
            }
            return Convert.ToBase64String(encrypted);
        }