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freebsd
GitHub Repository: freebsd/pkg
 Path: blob/main/external/libecc/src/curves/ec_shortw.c
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/*

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 *  Copyright (C) 2017 - This file is part of libecc project

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 *

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 *  Authors:

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 *      Ryad BENADJILA <[email protected]>

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 *      Arnaud EBALARD <[email protected]>

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 *      Jean-Pierre FLORI <[email protected]>

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 *

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 *  Contributors:

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 *      Nicolas VIVET <[email protected]>

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 *      Karim KHALFALLAH <[email protected]>

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 *

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 *  This software is licensed under a dual BSD and GPL v2 license.

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 *  See LICENSE file at the root folder of the project.

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 */

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#include <libecc/curves/ec_shortw.h>

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#define EC_SHORTW_CRV_MAGIC ((word_t)(0x9c7c46a1a04c6720ULL))

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/*

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 * Check pointed short Weierstrass curve structure has already been

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 * initialized. Returns -1 on error, 0 on success.

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 */

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int ec_shortw_crv_check_initialized(ec_shortw_crv_src_t crv)

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{

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	int ret;

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	MUST_HAVE((crv != NULL) && (crv->magic == EC_SHORTW_CRV_MAGIC), ret, err);

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	ret = 0;

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err:

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	return ret;

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}

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/*

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 * Initialize pointed short Weierstrass curve structure using given a and b

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 * Fp elements representing curve equation (y^2 = x^3 + ax + b) parameters.

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 * 'order' parameter is the generator point order. The function returns 0

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 * on success, -1 on error.

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 */

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int ec_shortw_crv_init(ec_shortw_crv_t crv, fp_src_t a, fp_src_t b, nn_src_t order)

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{

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	fp tmp, tmp2;

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	int ret, iszero;

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	tmp.magic = tmp2.magic = WORD(0);

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	ret = nn_check_initialized(order); EG(ret, err);

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	ret = fp_check_initialized(a); EG(ret, err);

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	ret = fp_check_initialized(b); EG(ret, err);

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	MUST_HAVE((a->ctx == b->ctx), ret, err);

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	MUST_HAVE((crv != NULL), ret, err);

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	/* The discriminant (4 a^3 + 27 b^2) must be non zero */

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	ret = fp_init(&tmp, a->ctx); EG(ret, err);

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	ret = fp_init(&tmp2, a->ctx); EG(ret, err);

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	ret = fp_sqr(&tmp, a); EG(ret, err);

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	ret = fp_mul(&tmp, &tmp, a); EG(ret, err);

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	ret = fp_set_word_value(&tmp2, WORD(4)); EG(ret, err);

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	ret = fp_mul(&tmp, &tmp, &tmp2); EG(ret, err);

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	ret = fp_set_word_value(&tmp2, WORD(27)); EG(ret, err);

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	ret = fp_mul(&tmp2, &tmp2, b); EG(ret, err);

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	ret = fp_mul(&tmp2, &tmp2, b); EG(ret, err);

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	ret = fp_add(&tmp, &tmp, &tmp2); EG(ret, err);

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	ret = fp_iszero(&tmp, &iszero); EG(ret, err);

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	MUST_HAVE((!iszero), ret, err);

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	ret = fp_init(&(crv->a), a->ctx); EG(ret, err);

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	ret = fp_init(&(crv->b), b->ctx); EG(ret, err);

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	ret = fp_init(&(crv->a_monty), a->ctx); EG(ret, err);

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	ret = fp_copy(&(crv->a), a); EG(ret, err);

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	ret = fp_copy(&(crv->b), b); EG(ret, err);

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	ret = fp_redcify(&(crv->a_monty), a); EG(ret, err);

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	ret = nn_copy(&(crv->order), order); EG(ret, err);

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#ifndef NO_USE_COMPLETE_FORMULAS

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	ret = fp_init(&(crv->b3), b->ctx); EG(ret, err);

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	ret = fp_init(&(crv->b_monty), b->ctx); EG(ret, err);

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	ret = fp_init(&(crv->b3_monty), b->ctx); EG(ret, err);

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	ret = fp_add(&(crv->b3), b, b); EG(ret, err);

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	ret = fp_add(&(crv->b3), &(crv->b3), b); EG(ret, err);

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	ret = fp_redcify(&(crv->b_monty), b); EG(ret, err);

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	ret = fp_redcify(&(crv->b3_monty), &(crv->b3)); EG(ret, err);

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#endif

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	crv->magic = EC_SHORTW_CRV_MAGIC;

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err:

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	fp_uninit(&tmp);

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	fp_uninit(&tmp2);

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	return ret;

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}

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/* Uninitialize curve */

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void ec_shortw_crv_uninit(ec_shortw_crv_t crv)

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{

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	if((crv != NULL) && (crv->magic == EC_SHORTW_CRV_MAGIC)){

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		crv->magic = WORD(0);

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	}

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	return;

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}

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