/*

 * XMSS WOTS Parameters

 * (C) 2016,2018 Matthias Gierlings

 *

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

 **/

#ifndef BOTAN_XMSS_WOTS_PARAMETERS_H_

#define BOTAN_XMSS_WOTS_PARAMETERS_H_

#include <botan/xmss_tools.h>

#include <botan/secmem.h>

#include <map>

#include <string>

namespace Botan {

/**

 * Descibes a signature method for XMSS Winternitz One Time Signatures,

 * as defined in:

 * [1] XMSS: Extended Hash-Based Signatures,

 *     Request for Comments: 8391

 *     Release: May 2018.

 *     https://datatracker.ietf.org/doc/rfc8391/

 **/

class XMSS_WOTS_Parameters final

   {

   public:

      enum ots_algorithm_t

         {

         WOTSP_SHA2_256 = 0x00000001,

         WOTSP_SHA2_512 = 0x00000002,

         WOTSP_SHAKE_256 = 0x00000003,

         WOTSP_SHAKE_512 = 0x00000004

         };

      XMSS_WOTS_Parameters(const std::string& algo_name);

      XMSS_WOTS_Parameters(ots_algorithm_t ots_spec);

      static ots_algorithm_t xmss_wots_id_from_string(const std::string& param_set);

      /**

       * Algorithm 1: convert input string to base.

       *

       * @param msg Input string (referred to as X in [1]).

       * @param out_size size of message in base w.

       *

       * @return Input string converted to the given base.

       **/

      secure_vector<uint8_t> base_w(const secure_vector<uint8_t>& msg, size_t out_size) const;

      secure_vector<uint8_t> base_w(size_t value) const;

      void append_checksum(secure_vector<uint8_t>& data);

      /**

       * @return XMSS WOTS registry name for the chosen parameter set.

       **/

      const std::string& name() const

         {

         return m_name;

         }

      /**

       * @return Botan name for the hash function used.

       **/

      const std::string& hash_function_name() const

         {

         return m_hash_name;

         }

      /**

       * Retrieves the uniform length of a message, and the size of

       * each node. This correlates to XMSS parameter "n" defined

       * in [1].

       *

       * @return element length in bytes.

       **/

      size_t element_size() const { return m_element_size; }

      /**

       * The Winternitz parameter.

       *

       * @return numeric base used for internal representation of

       *         data.

       **/

      size_t wots_parameter() const { return m_w; }

      size_t len() const { return m_len; }

      size_t len_1() const { return m_len_1; }

      size_t len_2() const { return m_len_2; }

      size_t lg_w() const { return m_lg_w; }

      ots_algorithm_t oid() const { return m_oid; }

      size_t estimated_strength() const { return m_strength; }

      bool operator==(const XMSS_WOTS_Parameters& p) const

         {

         return m_oid == p.m_oid;

         }

   private:

      static const std::map<std::string, ots_algorithm_t> m_oid_name_lut;

      ots_algorithm_t m_oid;

      std::string m_name;

      std::string m_hash_name;

      size_t m_element_size;

      size_t m_w;

      size_t m_len_1;

      size_t m_len_2;

      size_t m_len;

      size_t m_strength;

      uint8_t m_lg_w;

   };

}

#endif