libbrandt/smc.c

/* This file is part of libbrandt.
 * Copyright (C) 2016 GNUnet e.V.
 *
 * libbrandt is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * libbrandt is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * libbrandt.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * @file smc.c
 * @brief Implementation of the smc primitives.
 */

#include "util.h"

#include <pari/pari.h>

GEN
smc_hextodec (const char *s)                      /* int */
{
	size_t i;
	char c;
	pari_sp ltop = avma;
	GEN ret = gen_0;                        /* int */

	for (i = 0; i < strlen (s); i++)
	{
		errno = 0;
		if (1 != sscanf (&s[i], "%1hhx", &c))
		{
			brandt_eprintf ("failed to parse hex (\"%s\") to decimal:", s);
			return NULL;
		}
		ret = addis (shifti (ret, 4), c);
	}
	return gerepilecopy (ltop, ret);
}


void
smc_genbid (struct AuctionData *ad, uint16_t bid)
{
	uint16_t j;
	pari_sp ltop = avma;
	GEN ret = cgetg (itos (ad->k)+1, t_VEC);         /* vec */

	for (j = 1; j <= ad->k; j++)
	{
		gel (ret, j) = gpowgs (ad->g, bid == j);
	}
	ad->b = gerepilecopy (ltop, ret);
}


void
smc_genalpha (struct AuctionData *ad)
{
	uint16_t j;
	pari_sp ltop = avma;
	GEN ret = cgetg (ad->k+1, t_VEC);

	for (j = 1; j <= ad->k; ++j)
	{
		gel (ret, j) = gmul (gel (ad->b, j), gpowgi (ad->y, gel (ad->r, j)));
	}
	ad->alpha = gerepilecopy (ltop, ret);
}


void
smc_genbeta (struct AuctionData *ad)
{
	uint16_t j;
	pari_sp ltop = avma;
	GEN ret = cgetg (ad->k+1, t_VEC);

	for (j = 1; j <= ad->k; ++j)
	{
		gel (ret, j) = gpowgi (ad->g, gel (ad->r, j));
	}
	ad->beta = gerepilecopy (ltop, ret);
}