/*

* Comb4P hash combiner

* (C) 2010 Jack Lloyd

*

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

*/

#ifndef BOTAN_COMB4P_H_

#define BOTAN_COMB4P_H_

#include <botan/hash.h>

namespace Botan {

/**

* Combines two hash functions using a Feistel scheme. Described in

* "On the Security of Hash Function Combiners", Anja Lehmann

*/

class Comb4P final : public HashFunction

   {

   public:

      /**

      * @param h1 the first hash

      * @param h2 the second hash

      */

      Comb4P(std::unique_ptr<HashFunction> h1, std::unique_ptr<HashFunction> h2);

      size_t hash_block_size() const override;

      size_t output_length() const override

         {

         return m_hash1->output_length() + m_hash2->output_length();

         }

      std::unique_ptr<HashFunction> new_object() const override

         {

         return std::make_unique<Comb4P>(m_hash1->new_object(), m_hash2->new_object());

         }

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

      std::string name() const override

         {

         return "Comb4P(" + m_hash1->name() + "," + m_hash2->name() + ")";

         }

      void clear() override;

   private:

      Comb4P() = default;

      void add_data(const uint8_t input[], size_t length) override;

      void final_result(uint8_t out[]) override;

      std::unique_ptr<HashFunction> m_hash1, m_hash2;

   };

}

#endif