int HDLOG_challenge_CG21()

in src/hidden_dlog.c [143:197]

• 37 lines of code
• 3 McCabe index (conditional complexity)

int HDLOG_challenge_CG21(BIG_1024_58 *N, BIG_1024_58 *B0, BIG_1024_58 *B1, HDLOG_iter_values RHO, const HDLOG_SSID *ssid,
                         octet *E, int n)
{
    hash256 sha;
    char o[SFS_SECP256K1 + 1];
    octet G_oct = {0, sizeof(o), o};

    char qq[EGS_SECP256K1];
    octet q_oct = {0, sizeof(qq), qq};


    char w[FS_2048];
    octet W = {0, sizeof(w), w};

    HASH256_init(&sha);

    // Bind the public parameters
    FF_2048_toOctet(&W, N, FFLEN_2048);
    HASH_UTILS_hash_oct(&sha, &W);

    FF_2048_toOctet(&W, B0, FFLEN_2048);
    HASH_UTILS_hash_oct(&sha, &W);

    FF_2048_toOctet(&W, B1, FFLEN_2048);
    HASH_UTILS_hash_oct(&sha, &W);

    HASH_UTILS_hash_oct(&sha, ssid->rid);
    HASH_UTILS_hash_oct(&sha, ssid->rho);

    CG21_get_G(&G_oct);
    CG21_get_q(&q_oct);

    HASH_UTILS_hash_oct(&sha, &G_oct);
    HASH_UTILS_hash_oct(&sha, &q_oct);

    // sort partial X[i] based on j_packed and process them into sha
    int rc = CG21_hash_set_X(&sha, ssid->X_set_packed, ssid->j_set_packed, n, EFS_SECP256K1 + 1);
    if (rc!=CG21_OK){
        return rc;
    }

    // Bind to commitment
    for (int i = 0; i < HDLOG_PROOF_ITERS; i++)
    {
        FF_2048_toOctet(&W, RHO[i], FFLEN_2048);
        HASH_UTILS_hash_oct(&sha, &W);
    }

    HASH256_hash(&sha, w);

    OCT_clear(E);
    OCT_jbytes(E, w, HDLOG_CHALLENGE_SIZE);

    return HDLOG_OK;
}