xmss_signature.cpp

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/*
 * XMSS Signature
 * (C) 2016,2017,2018 Matthias Gierlings
 *
 * Botan is released under the Simplified BSD License (see license.txt)
 **/
 
#include <botan/internal/xmss_signature.h>
#include <iterator>
 
namespace Botan {
 
XMSS_Signature::XMSS_Signature(XMSS_Parameters::xmss_algorithm_t oid,
                               const secure_vector<uint8_t>& raw_sig)
   : m_leaf_idx(0), m_randomness(0, 0x00), m_tree_sig()
   {
   XMSS_Parameters xmss_params(oid);
 
   if(raw_sig.size() != (xmss_params.len() + xmss_params.tree_height() + 1)
                        * xmss_params.element_size() + sizeof(uint32_t))
   {
      throw Decoding_Error("XMSS signature size invalid.");
   }
 
   for(size_t i = 0; i < 4; i++)
      { m_leaf_idx = ((m_leaf_idx << 8) | raw_sig[i]); }
 
   if(m_leaf_idx >= (1ull << xmss_params.tree_height()))
      {
      throw Decoding_Error("XMSS signature leaf index out of bounds.");
      }
 
   auto begin = raw_sig.begin() + sizeof(uint32_t);
   auto end = begin + xmss_params.element_size();
   std::copy(begin, end, std::back_inserter(m_randomness));
 
   for(size_t i = 0; i < xmss_params.len(); i++)
      {
      begin = end;
      end = begin + xmss_params.element_size();
      m_tree_sig.ots_signature().push_back(secure_vector<uint8_t>(0));
      m_tree_sig.ots_signature().back().reserve(
         xmss_params.element_size());
      std::copy(begin,
                end,
                std::back_inserter(m_tree_sig.ots_signature().back()));
      }
 
   for(size_t i = 0; i < xmss_params.tree_height(); i++)
      {
      begin = end;
      end = begin + xmss_params.element_size();
      m_tree_sig.authentication_path().push_back(secure_vector<uint8_t>(0));
      m_tree_sig.authentication_path().back().reserve(
         xmss_params.element_size());
      std::copy(begin,
                end,
                std::back_inserter(m_tree_sig.authentication_path().back()));
      }
   }
 
secure_vector<uint8_t> XMSS_Signature::bytes() const
   {
   secure_vector<uint8_t> result
      {
      static_cast<uint8_t>(m_leaf_idx >> 24U),
      static_cast<uint8_t>(m_leaf_idx >> 16U),
      static_cast<uint8_t>(m_leaf_idx >>  8U),
      static_cast<uint8_t>(m_leaf_idx)
      };
 
   std::copy(m_randomness.begin(),
             m_randomness.end(),
             std::back_inserter(result));
 
   for(const auto& sig : tree().ots_signature())
      {
      std::copy(sig.begin(),
                sig.end(),
                std::back_inserter(result));
      }
 
   for(const auto& auth : tree().authentication_path())
      {
      std::copy(auth.begin(),
                auth.end(),
                std::back_inserter(result));
      }
   return result;
   }
 
}