AaltoTLS.RecordLayer.RecordHandler.GenerateMAC C# (CSharp) Method

        private static void GenerateMAC(CipherSuite cipherSuite, Record record, UInt64 seqNum, KeyedHashAlgorithm hasher)
        {
            BulkCipherAlgorithmType cipherType = cipherSuite.BulkCipherAlgorithm.Type;

            if (cipherType == BulkCipherAlgorithmType.Stream || cipherType == BulkCipherAlgorithmType.Block) {
                byte[] additional = GetAdditionalBytes(seqNum, record.Type, record.Version, record.Fragment.Length);

                // Calculate the MAC of the packet
                hasher.Initialize();
                hasher.TransformBlock(additional, 0, additional.Length, additional, 0);
                hasher.TransformFinalBlock(record.Fragment, 0, record.Fragment.Length);
                byte[] MAC = hasher.Hash;

                /* Add MAC to the end of the fragment */
                byte[] fragment = new byte[record.Fragment.Length + MAC.Length];
                Buffer.BlockCopy(record.Fragment, 0, fragment, 0, record.Fragment.Length);
                Buffer.BlockCopy(MAC, 0, fragment, record.Fragment.Length, MAC.Length);
                record.Fragment = fragment;
            }
        }