static char bds_state_update()

in xmss_fast.c [383:439]

• 48 lines of code
• 9 McCabe index (conditional complexity)

static char bds_state_update(bds_state *state, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, const uint32_t addr[8]) {
  uint32_t ltree_addr[8];
  uint32_t node_addr[8];
  uint32_t ots_addr[8];

  int n = params->n;
  int h = params->h;
  int k = params->k;

  int nodeh;
  int idx = state->next_leaf;
  if (idx == 1 << h) {
    return 1;
  }

  // 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);
  
  setOTSADRS(ots_addr, idx);
  setLtreeADRS(ltree_addr, idx);

  gen_leaf_wots(state->stack+state->stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr);

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

    state->stacklevels[state->stackoffset-2]++;
    state->stackoffset--;
  }
  state->next_leaf++;
  return 0;
}