static void validate_authpath()

in xmss_fast.c [296:339]

• 39 lines of code
• 10 McCabe index (conditional complexity)

static void validate_authpath(unsigned char *root, const unsigned char *leaf, unsigned long leafidx, const unsigned char *authpath, const xmss_params *params, const unsigned char *pub_seed, uint32_t addr[8])
{
  unsigned int n = params->n;

  uint32_t i, j;
  unsigned char buffer[2*n];

  // If leafidx is odd (last bit = 1), current path element is a right child and authpath has to go to the left.
  // Otherwise, it is the other way around
  if (leafidx & 1) {
    for (j = 0; j < n; j++)
      buffer[n+j] = leaf[j];
    for (j = 0; j < n; j++)
      buffer[j] = authpath[j];
  }
  else {
    for (j = 0; j < n; j++)
      buffer[j] = leaf[j];
    for (j = 0; j < n; j++)
      buffer[n+j] = authpath[j];
  }
  authpath += n;

  for (i=0; i < params->h-1; i++) {
    setTreeHeight(addr, i);
    leafidx >>= 1;
    setTreeIndex(addr, leafidx);
    if (leafidx&1) {
      hash_h(buffer+n, buffer, pub_seed, addr, n);
      for (j = 0; j < n; j++)
        buffer[j] = authpath[j];
    }
    else {
      hash_h(buffer, buffer, pub_seed, addr, n);
      for (j = 0; j < n; j++)
        buffer[j+n] = authpath[j];
    }
    authpath += n;
  }
  setTreeHeight(addr, (params->h-1));
  leafidx >>= 1;
  setTreeIndex(addr, leafidx);
  hash_h(root, buffer, pub_seed, addr, n);
}