Coverage Report

Created: 2021-02-21 07:20

/src/botan/src/lib/pubkey/xmss/xmss_wots_parameters.cpp
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/*
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 * XMSS WOTS Parameters
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 * Descibes a signature method for XMSS Winternitz One Time Signatures,
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 * as defined in:
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 * [1] XMSS: Extended Hash-Based Signatures,
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 *     Request for Comments: 8391
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 *     Release: May 2018.
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 *     https://datatracker.ietf.org/doc/rfc8391/
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 *
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 * (C) 2016,2017,2018 Matthias Gierlings
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 *
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 * Botan is released under the Simplified BSD License (see license.txt)
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 **/
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#include <botan/xmss_wots.h>
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#include <botan/internal/xmss_tools.h>
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#include <botan/exceptn.h>
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#include <cmath>
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namespace Botan {
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XMSS_WOTS_Parameters::ots_algorithm_t
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XMSS_WOTS_Parameters::xmss_wots_id_from_string(const std::string& param_set)
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   {
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   if(param_set == "WOTSP-SHA2_256")
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      { return WOTSP_SHA2_256; }
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   if(param_set == "WOTSP-SHA2_512")
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      { return WOTSP_SHA2_512; }
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   if(param_set == "WOTSP-SHAKE_256")
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      { return WOTSP_SHAKE_256; }
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   if(param_set == "WOTSP-SHAKE_512")
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      { return WOTSP_SHAKE_512; }
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   throw Invalid_Argument("Unknown XMSS-WOTS algorithm param '" + param_set + "'");
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   }
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XMSS_WOTS_Parameters::XMSS_WOTS_Parameters(const std::string& param_set)
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   : XMSS_WOTS_Parameters(xmss_wots_id_from_string(param_set))
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   {}
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XMSS_WOTS_Parameters::XMSS_WOTS_Parameters(ots_algorithm_t oid)
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   : m_oid(oid)
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   {
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   switch(oid)
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      {
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      case WOTSP_SHA2_256:
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         m_element_size = 32;
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         m_w = 16;
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         m_len = 67;
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         m_name = "WOTSP-SHA2_256";
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         m_hash_name = "SHA-256";
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         m_strength = 256;
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         break;
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      case WOTSP_SHA2_512:
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         m_element_size = 64;
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         m_w = 16;
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         m_len = 131;
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         m_name = "WOTSP-SHA2_512";
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         m_hash_name = "SHA-512";
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         m_strength = 512;
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         break;
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      case WOTSP_SHAKE_256:
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         m_element_size = 32;
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         m_w = 16;
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         m_len = 67;
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         m_name = "WOTSP-SHAKE_256";
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         m_hash_name = "SHAKE-128(256)";
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         m_strength = 256;
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         break;
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      case WOTSP_SHAKE_512:
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         m_element_size = 64;
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         m_w = 16;
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         m_len = 131;
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         m_name = "WOTSP-SHAKE_512";
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         m_hash_name = "SHAKE-256(512)";
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         m_strength = 512;
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         break;
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      default:
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         throw Not_Implemented("Algorithm id does not match any known XMSS WOTS algorithm id.");
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         break;
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      }
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   m_lg_w = (m_w == 16) ? 4 : 2;
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   m_len_1 = static_cast<size_t>(std::ceil((8 * element_size()) / m_lg_w));
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   m_len_2 = static_cast<size_t>(
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                floor(log2(m_len_1 * (wots_parameter() - 1)) / m_lg_w) + 1);
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   BOTAN_ASSERT(m_len == m_len_1 + m_len_2, "Invalid XMSS WOTS parameter "
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                "\"len\" detedted.");
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   }
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secure_vector<uint8_t>
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XMSS_WOTS_Parameters::base_w(const secure_vector<uint8_t>& msg, size_t out_size) const
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   {
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   secure_vector<uint8_t> result;
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   size_t in = 0;
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   size_t total = 0;
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   size_t bits = 0;
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   for(size_t i = 0; i < out_size; i++)
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      {
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      if(bits == 0)
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         {
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         total = msg[in];
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         in++;
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         bits += 8;
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         }
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      bits -= m_lg_w;
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      result.push_back(static_cast<uint8_t>((total >> bits) & (m_w - 1)));
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      }
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   return result;
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   }
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secure_vector<uint8_t>
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XMSS_WOTS_Parameters::base_w(size_t value) const
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   {
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   value <<= (8 - ((m_len_2 * m_lg_w) % 8));
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   size_t len_2_bytes = static_cast<size_t>(
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                           std::ceil(static_cast<float>(m_len_2 * m_lg_w) / 8.f));
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   secure_vector<uint8_t> result;
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   XMSS_Tools::concat(result, value, len_2_bytes);
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   return base_w(result, m_len_2);
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   }
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void
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XMSS_WOTS_Parameters::append_checksum(secure_vector<uint8_t>& data)
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   {
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   size_t csum = 0;
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   for(size_t i = 0; i < data.size(); i++)
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      {
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      csum += wots_parameter() - 1 - data[i];
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      }
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   secure_vector<uint8_t> csum_bytes = base_w(csum);
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   std::move(csum_bytes.begin(), csum_bytes.end(), std::back_inserter(data));
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   }
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}