ctr.hpp

/*
  ANCH Framework: ANother C++ Hack is a C++ framework based on C++11 standard
  Copyright (C) 2012 Vincent Lachenal

  This file is part of ANCH Framework.

  ANCH Framework is free software: you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  ANCH Framework is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with ANCH Framework.  If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _ANCH_CRYPTO_CTR_H_
#define _ANCH_CRYPTO_CTR_H_

#include "crypto/cipher/bcModOp.hpp"

namespace anch {
  namespace crypto {

    template<typename Cipher>
    class CTR: public BlockCipherModeOfOperation<CTR<Cipher>,Cipher> {

      // Attributes +
    private:
      std::array<uint8_t,Cipher::getBlockSize()> _nonce;
      // Attributes -


      // Constructors +
    public:
      CTR(const std::array<uint8_t,Cipher::getBlockSize()>& nonce, unsigned int nbThread = 1):
        BlockCipherModeOfOperation<CTR<Cipher>,Cipher>(true, true, nbThread),
        _nonce(nonce) {
        // Nothing to do
      }
      // Constructors -


      // Destructor +
      virtual ~CTR() {
        // Nothing to do
      }
      // Destructor -


      // Methods +
    protected:
      virtual std::size_t cipherBlock(std::array<uint8_t,Cipher::getBlockSize()>& input,
                                      std::streamsize nbRead,
                                      std::array<uint8_t,Cipher::getBlockSize()>& output,
                                      uint32_t index,
                                      Cipher& cipher) override {
        std::array<uint8_t,Cipher::getBlockSize()> ctxtVect(_nonce);
        uint16_t* counter = reinterpret_cast<uint16_t*>(&ctxtVect.data()[Cipher::getBlockSize() - 2]);
        *counter = index;
        std::array<uint8_t,Cipher::getBlockSize()> data;
        cipher.cipher(ctxtVect, data);
        for(std::streamsize i = 0 ; i < nbRead ; ++i) {
          output[i] = input[i] ^ data[i];
        }
        return nbRead;
      }

      virtual std::size_t decipherBlock(std::array<uint8_t,Cipher::getBlockSize()>& input,
                                        std::array<uint8_t,Cipher::getBlockSize()>&,
                                        std::streamsize nbRead,
                                        bool,
                                        std::array<uint8_t,Cipher::getBlockSize()>& output,
                                        uint32_t index,
                                        Cipher& cipher) override {
        std::array<uint8_t,Cipher::getBlockSize()> ctxtVect(_nonce);
        uint16_t* counter = reinterpret_cast<uint16_t*>(&ctxtVect.data()[Cipher::getBlockSize() - 2]);
        *counter = index;
        std::array<uint8_t,Cipher::getBlockSize()> data;
        cipher.cipher(ctxtVect, data);
        for(std::streamsize i = 0 ; i < nbRead ; ++i) {
          output[i] = input[i] ^ data[i];
        }
        return nbRead;
      }

      virtual const std::array<uint8_t,Cipher::getBlockSize()>& reset() {
        return _nonce;
      }
      // Methods -

    };

  }
}

#endif // _ANCH_CRYPTO_CTR_H_