ret_t decode()

in src/decode/decode.c [219:280]

• 46 lines of code
• 4 McCabe index (conditional complexity)

ret_t decode(OUT e_t *e, IN const ct_t *ct, IN const sk_t *sk)
{
  // Initialize the decode methods struct
  decode_ctx ctx;
  decode_ctx_init(&ctx);

  DEFER_CLEANUP(e_t black_e = {0}, e_cleanup);
  DEFER_CLEANUP(e_t gray_e = {0}, e_cleanup);

  DEFER_CLEANUP(pad_r_t c0 = {0}, pad_r_cleanup);
  DEFER_CLEANUP(pad_r_t h0 = {0}, pad_r_cleanup);
  pad_r_t pk = {0};

  // Pad ciphertext (c0), secret key (h0), and public key (h)
  c0.val = ct->c0;
  h0.val = sk->bin[0];
  pk.val = sk->pk;

  DEFER_CLEANUP(syndrome_t s = {0}, syndrome_cleanup);
  DMSG("  Computing s.\n");
  GUARD(compute_syndrome(&s, &c0, &h0, &ctx));
  ctx.dup(&s);

  // Reset (init) the error because it is xored in the find_err functions.
  bike_memset(e, 0, sizeof(*e));

  for(uint32_t iter = 0; iter < MAX_IT; iter++) {
    const uint8_t threshold = get_threshold(&s);

    DMSG("    Iteration: %d\n", iter);
    DMSG("    Weight of e: %lu\n",
         r_bits_vector_weight(&e->val[0]) + r_bits_vector_weight(&e->val[1]));
    DMSG("    Weight of syndrome: %lu\n", r_bits_vector_weight((r_t *)s.qw));

    find_err1(e, &black_e, &gray_e, &s, sk->wlist, threshold, &ctx);
    GUARD(recompute_syndrome(&s, &c0, &h0, &pk, e, &ctx));
#if defined(BGF_DECODER)
    if(iter >= 1) {
      continue;
    }
#endif
    DMSG("    Weight of e: %lu\n",
         r_bits_vector_weight(&e->val[0]) + r_bits_vector_weight(&e->val[1]));
    DMSG("    Weight of syndrome: %lu\n", r_bits_vector_weight((r_t *)s.qw));

    find_err2(e, &black_e, &s, sk->wlist, ((D + 1) / 2) + 1, &ctx);
    GUARD(recompute_syndrome(&s, &c0, &h0, &pk, e, &ctx));

    DMSG("    Weight of e: %lu\n",
         r_bits_vector_weight(&e->val[0]) + r_bits_vector_weight(&e->val[1]));
    DMSG("    Weight of syndrome: %lu\n", r_bits_vector_weight((r_t *)s.qw));

    find_err2(e, &gray_e, &s, sk->wlist, ((D + 1) / 2) + 1, &ctx);
    GUARD(recompute_syndrome(&s, &c0, &h0, &pk, e, &ctx));
  }

  if(r_bits_vector_weight((r_t *)s.qw) > 0) {
    BIKE_ERROR(E_DECODING_FAILURE);
  }

  return SUCCESS;
}