public static SymmetricAlgorithm GetSymmetricAlgorithm(string algorithm)
        {
            var symmetric = null as SymmetricAlgorithm;

            if (AesEncryption.Contains(algorithm))
            {
                symmetric = Aes.Create();
            }

            if (symmetric == null)
            {
                throw new NotSupportedException($"Encryption algorithm '{algorithm}' not supported.");
            }

            symmetric.Mode    = GetCipherMode(algorithm);
            symmetric.Padding = PaddingMode.ISO10126;
            symmetric.KeySize = GetKeySize(algorithm);
            symmetric.GenerateKey();
            symmetric.GenerateIV();

            return(symmetric);
        }