Appending IV to an

Question

I am in the process of writing a small encoding class which takes a byte[] array, and cyphers it. As the IV can be made public, I wish to prepend it to the ciphertext to use for decryption.

Following the MSDN Documentation and some SO Post source (Cant find link), I started the stream with the raw IV;

//Start encryption process
        using (var msEncrypt = new MemoryStream())
        {
            using (var csEncrypt = new CryptoStream(msEncrypt, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
            {
                using (var swWriter = new StreamWriter(csEncrypt))
                {

                    //Write all data to the stream.
                    swWriter.Write(encryptor.IV);
                    swWriter.Write(plainTextRaw);



                }

            }

            Console.WriteLine("Encrypted Value: {0}", BitConverter.ToString(msEncrypt.ToArray()).Replace("-", String.Empty));
            return msEncrypt.ToArray();

        }

However, upon writing a simple unit test extracting the first 16 bytes, they do not seem to match.

I am certain the IV is being encrypted within the stream, so where is the best place to inject it?

Answer 1

Just write the IV tot the initial memory stream msEncrypt, not to the stream that is being encrypted swWriter.