static void treehash_setup()

in xmss_fast.c [178:247]

• 62 lines of code
• 11 McCabe index (conditional complexity)

static void treehash_setup(unsigned char *node, int height, int index, bds_state *state, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const uint32_t addr[8])
{
  unsigned int idx = index;
  unsigned int n = params->n;
  unsigned int h = params->h;
  unsigned int k = params->k;
  // use three different addresses because at this point we use all three formats in parallel
  uint32_t ots_addr[8];
  uint32_t ltree_addr[8];
  uint32_t  node_addr[8];
  // only copy layer and tree address parts
  memcpy(ots_addr, addr, 12);
  // type = ots
  setType(ots_addr, 0);
  memcpy(ltree_addr, addr, 12);
  setType(ltree_addr, 1);
  memcpy(node_addr, addr, 12);
  setType(node_addr, 2);

  uint32_t lastnode, i;
  unsigned char stack[(height+1)*n];
  unsigned int stacklevels[height+1];
  unsigned int stackoffset=0;
  unsigned int nodeh;

  lastnode = idx+(1<<height);

  for (i = 0; i < h-k; i++) {
    state->treehash[i].h = i;
    state->treehash[i].completed = 1;
    state->treehash[i].stackusage = 0;
  }

  i = 0;
  for (; idx < lastnode; idx++) {
    setLtreeADRS(ltree_addr, idx);
    setOTSADRS(ots_addr, idx);
    gen_leaf_wots(stack+stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr);
    stacklevels[stackoffset] = 0;
    stackoffset++;
    if (h - k > 0 && i == 3) {
      memcpy(state->treehash[0].node, stack+stackoffset*n, n);
    }
    while (stackoffset>1 && stacklevels[stackoffset-1] == stacklevels[stackoffset-2])
    {
      nodeh = stacklevels[stackoffset-1];
      if (i >> nodeh == 1) {
        memcpy(state->auth + nodeh*n, stack+(stackoffset-1)*n, n);
      }
      else {
        if (nodeh < h - k && i >> nodeh == 3) {
          memcpy(state->treehash[nodeh].node, stack+(stackoffset-1)*n, n);
        }
        else if (nodeh >= h - k) {
          memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((i >> nodeh) - 3) >> 1)) * n, stack+(stackoffset-1)*n, n);
        }
      }
      setTreeHeight(node_addr, stacklevels[stackoffset-1]);
      setTreeIndex(node_addr, (idx >> (stacklevels[stackoffset-1]+1)));
      hash_h(stack+(stackoffset-2)*n, stack+(stackoffset-2)*n, pub_seed,
          node_addr, n);
      stacklevels[stackoffset-2]++;
      stackoffset--;
    }
    i++;
  }

  for (i = 0; i < n; i++)
    node[i] = stack[i];
}