/*

 * XOF based on AES-256/CTR for CRYSTALS Kyber/Dilithium 90s-modes

 * (C) 2023 Jack Lloyd

 *     2023 René Meusel - Rohde & Schwarz Cybersecurity

 *

 * Botan is released under the Simplified BSD License (see license.txt)

 */

#ifndef BOTAN_AES_CRYSTALS_XOF_H_

#define BOTAN_AES_CRYSTALS_XOF_H_

#include <botan/secmem.h>

#include <botan/xof.h>

namespace Botan {

class StreamCipher;

/**

 * XOF implementation for Kyber/Dilithium 90s-modes based on

 * AES-256 in counter mode.

 *

 * This is an internal class that is not meant for consumption

 * by library users. It is therefore not registered in XOF::create().

 */

class BOTAN_TEST_API AES_256_CTR_XOF final : public XOF {

   public:

      AES_256_CTR_XOF();

      ~AES_256_CTR_XOF() override;

      void reset() override;

      std::string name() const override { return "CTR-BE(AES-256)"; }

      /**

       * Checks that the given @p iv_length is compatible with this XOF

       */

      bool valid_salt_length(size_t iv_length) const override;

      Key_Length_Specification key_spec() const override;

      size_t block_size() const override { return 16; }

      std::unique_ptr<XOF> copy_state() const override;

      std::unique_ptr<XOF> new_object() const override { return std::make_unique<AES_256_CTR_XOF>(); }

      bool accepts_input() const override { return false; }

   private:

      /**

       * Sets the @p IV and @p key of the underlying AES-256/CTR object.

       * Do not call AES_256_CTR_XOF::update(), on this object!

       */

      void start_msg(std::span<const uint8_t> iv = {}, std::span<const uint8_t> key = {}) override;

      /**

       * @throws Not_Implemented, use XOF::start() instead of XOF::update()

       */

      void add_data(std::span<const uint8_t>) override;

      void generate_bytes(std::span<uint8_t> output) override;

   private:

      std::unique_ptr<StreamCipher> m_stream_cipher;

};

}  // namespace Botan

#endif