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, std::span<const uint8_t> raw_sig) :
      m_leaf_idx(0), m_randomness(0, 0x00) {
   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 >= xmss_params.total_number_of_signatures()) {
      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()));
   }
}
 
std::vector<uint8_t> XMSS_Signature::bytes() const {
   std::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;
}
 
}  // namespace Botan