internal interface Cipher
  {
    void Encrypt(byte[] data, int offset, int len, byte[] result, int result_offset);
    void Decrypt(byte[] data, int offset, int len, byte[] result, int result_offset);
    int BlockSize { get; }
  }

public class AES128CTR : Cipher
{
  private System.Security.Cryptography.ICryptoTransform Encryptor;
  private ArraySegment<Byte> _counter;

  public AES128CTR(byte[] key, byte[] iv)
  {
    _counter = new ArraySegment<byte>(iv);
    Encryptor = new SecurityDriven.Inferno.Cipher.AesCtrCryptoTransform(key, _counter);
  }

  public int BlockSize { get { return Encryptor.InputBlockSize; } }

  public void Decrypt(byte[] data, int offset, int len, byte[] result, int result_offset)
  {
    Encryptor.TransformBlock(data, 0, len, result, 0);
  }

  public void Encrypt(byte[] data, int offset, int len, byte[] result, int   result_offset)
  {
    Encryptor.TransformBlock(data, 0, len, result, 0);
  }
}