/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mpi.h"
#include "mplogic.h"
#include "ecl.h"
#include "ecp.h"
#include "ecl-priv.h"

#include <sys/types.h>
#include <stdio.h>
#include <time.h>
#include <sys/time.h>
#include <sys/resource.h>

/* Returns 2^e as an integer. This is meant to be used for small powers of
 * two. */
int ec_twoTo(int e);

/* Number of bits of scalar to test */
#define BITSIZE 160

/* Time k repetitions of operation op. */
#define M_TimeOperation(op, k)                                                        \
    {                                                                                 \
        double dStart, dNow, dUserTime;                                               \
        struct rusage ru;                                                             \
        int i;                                                                        \
        getrusage(RUSAGE_SELF, &ru);                                                  \
        dStart = (double)ru.ru_utime.tv_sec + (double)ru.ru_utime.tv_usec * 0.000001; \
        for (i = 0; i < k; i++) {                                                     \
            {                                                                         \
                op;                                                                   \
            }                                                                         \
        };                                                                            \
        getrusage(RUSAGE_SELF, &ru);                                                  \
        dNow = (double)ru.ru_utime.tv_sec + (double)ru.ru_utime.tv_usec * 0.000001;   \
        dUserTime = dNow - dStart;                                                    \
        if (dUserTime)                                                                \
            printf("    %-45s\n      k: %6i, t: %6.2f sec\n", #op, k, dUserTime);     \
    }

/* Tests wNAF computation. Non-adjacent-form is discussed in the paper: D.
 * Hankerson, J. Hernandez and A. Menezes, "Software implementation of
 * elliptic curve cryptography over binary fields", Proc. CHES 2000. */

mp_err
main(void)
{
    signed char naf[BITSIZE + 1];
    ECGroup *group = NULL;
    mp_int k;
    mp_int *scalar;
    int i, count;
    int res;
    int w = 5;
    char s[1000];

    /* Get a 160 bit scalar to compute wNAF from */
    group = ECGroup_fromName(ECCurve_SECG_PRIME_160R1);
    scalar = &group->genx;

    /* Compute wNAF representation of scalar */
    ec_compute_wNAF(naf, BITSIZE, scalar, w);

    /* Verify correctness of representation */
    mp_init(&k); /* init k to 0 */

    for (i = BITSIZE; i >= 0; i--) {
        mp_add(&k, &k, &k);
        /* digits in mp_???_d are unsigned */
        if (naf[i] >= 0) {
            mp_add_d(&k, naf[i], &k);
        } else {
            mp_sub_d(&k, -naf[i], &k);
        }
    }

    if (mp_cmp(&k, scalar) != 0) {
        printf("Error:  incorrect NAF value.\n");
        MP_CHECKOK(mp_toradix(&k, s, 16));
        printf("NAF value   %s\n", s);
        MP_CHECKOK(mp_toradix(scalar, s, 16));
        printf("original value   %s\n", s);
        goto CLEANUP;
    }

    /* Verify digits of representation are valid */
    for (i = 0; i <= BITSIZE; i++) {
        if (naf[i] % 2 == 0 && naf[i] != 0) {
            printf("Error:  Even non-zero digit found.\n");
            goto CLEANUP;
        }
        if (naf[i] < -(ec_twoTo(w - 1)) || naf[i] >= ec_twoTo(w - 1)) {
            printf("Error:  Magnitude of naf digit too large.\n");
            goto CLEANUP;
        }
    }

    /* Verify sparsity of representation */
    count = w - 1;
    for (i = 0; i <= BITSIZE; i++) {
        if (naf[i] != 0) {
            if (count < w - 1) {
                printf("Error:  Sparsity failed.\n");
                goto CLEANUP;
            }
            count = 0;
        } else
            count++;
    }

    /* Check timing */
    M_TimeOperation(ec_compute_wNAF(naf, BITSIZE, scalar, w), 10000);

    printf("Test passed.\n");
CLEANUP:
    ECGroup_free(group);
    return MP_OKAY;
}