/*

 * XMSS Common Ops

 * Operations shared by XMSS signature generation and verification operations.

 * (C) 2016,2017 Matthias Gierlings

 *

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

 **/

#include <botan/internal/xmss_common_ops.h>

#include <botan/xmss_hash.h>

namespace Botan {

void

XMSS_Common_Ops::randomize_tree_hash(secure_vector<uint8_t>& result,

                                     const secure_vector<uint8_t>& left,

                                     const secure_vector<uint8_t>& right,

                                     XMSS_Address& adrs,

                                     const secure_vector<uint8_t>& seed,

                                     XMSS_Hash& hash,

                                     const XMSS_Parameters& params)

   {

   adrs.set_key_mask_mode(XMSS_Address::Key_Mask::Key_Mode);

   secure_vector<uint8_t> key { hash.prf(seed, adrs.bytes()) };

   adrs.set_key_mask_mode(XMSS_Address::Key_Mask::Mask_MSB_Mode);

   secure_vector<uint8_t> bitmask_l { hash.prf(seed, adrs.bytes()) };

   adrs.set_key_mask_mode(XMSS_Address::Key_Mask::Mask_LSB_Mode);

   secure_vector<uint8_t> bitmask_r { hash.prf(seed, adrs.bytes()) };

   BOTAN_ASSERT(bitmask_l.size() == left.size() &&

                bitmask_r.size() == right.size(),

                "Bitmask size doesn't match node size.");

   secure_vector<uint8_t> concat_xor(params.element_size() * 2);

   for(size_t i = 0; i < left.size(); i++)

      {

      concat_xor[i] = left[i] ^ bitmask_l[i];

      concat_xor[i + left.size()] = right[i] ^ bitmask_r[i];

      }

   hash.h(result, key, concat_xor);

   }

void

XMSS_Common_Ops::create_l_tree(secure_vector<uint8_t>& result,

                               wots_keysig_t pk,

                               XMSS_Address& adrs,

                               const secure_vector<uint8_t>& seed,

                               XMSS_Hash& hash,

                               const XMSS_Parameters& params)

   {

   size_t l = params.len();

   adrs.set_tree_height(0);

   while(l > 1)

      {

      for(size_t i = 0; i < l >> 1; i++)

         {

         adrs.set_tree_index(static_cast<uint32_t>(i));

         randomize_tree_hash(pk[i], pk[2 * i], pk[2 * i + 1], adrs, seed, hash, params);

         }

      if(l & 0x01)

         {

         pk[l >> 1] = pk[l - 1];

         }

      l = (l >> 1) + (l & 0x01);

      adrs.set_tree_height(adrs.get_tree_height() + 1);

      }

   result = pk[0];

   }

}