AesProvider

public class AesProvider : ISymetricProvider
    {
        private readonly RijndaelManaged _sa = new RijndaelManaged()
        {
            Mode = CipherMode.CBC
        };

        private const int SymmetricKeyLength = 32;

        public byte[] Encrypt(byte[] bytes, byte[] key)
        {
            var iv = ScaleVector(key, 16);
            if (key.Length != SymmetricKeyLength) key = ScaleVector(key, SymmetricKeyLength);


            using (var encryptor = _sa.CreateEncryptor(key, iv))
            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(bytes, 0, bytes.Length);
                }
                return memoryStream.ToArray();
            }
        }

        public byte[] Decrypt(byte[] bytes, byte[] key)
        {
            var iv = ScaleVector(key, 16);

            using (var decryptor = _sa.CreateDecryptor(key, iv))
            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(bytes, 0, bytes.Length);
                }
                return memoryStream.ToArray();
            }
        }

        private static byte[] ScaleVector(IReadOnlyList<byte> vector, int newLength)
        {
            if (vector == null) throw new ArgumentNullException();
            if (vector.Count < 1) throw new ArgumentException("Key too short");

            var result = new byte[newLength];
            var multiplier = (newLength << 16) / vector.Count;

            for (var i = 0; i < newLength; i++)
            {
                var m = i * multiplier;
                result[i] = (byte)(vector[m >> 16] ^ (byte)m);
            }

            return result;
        }
    }