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freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/crypto/libecc/src/curves/ec_montgomery.c
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/*

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 *  Copyright (C) 2021 - 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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 *

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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_montgomery.h>

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#define EC_MONTGOMERY_CRV_MAGIC ((word_t)(0x83734673a0443720ULL))

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/* Check if a Montgomery curve is initialized.

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 * Returns 0 on success, -1 on error.

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 */

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int ec_montgomery_crv_check_initialized(ec_montgomery_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_MONTGOMERY_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 Montgomery curve structure using given A and B

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 * Fp elements representing curve equation (B v^2 = u^3 + A u^2 + u) parameters.

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 *

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 * The function returns 0 on success, -1 on error.

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 */

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int ec_montgomery_crv_init(ec_montgomery_crv_t crv, fp_src_t A, fp_src_t B, nn_src_t order)

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{

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	int ret, iszero;

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	fp tmp;

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	tmp.magic = WORD(0);

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

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

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	/* A and B elements of Fp, A unequal to (+/-)2 and B non zero */

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	ret = fp_set_word_value(&tmp, 2); EG(ret, err);

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

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	MUST_HAVE((!fp_iszero(&tmp, &iszero)) && (!iszero), ret, err);

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	ret = fp_set_word_value(&tmp, 2); EG(ret, err);

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	ret = fp_sub(&tmp, A, &tmp); EG(ret, err);

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	MUST_HAVE((!fp_iszero(&tmp, &iszero)) && (!iszero), ret, err);

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	MUST_HAVE((!fp_iszero(B, &iszero)) && (!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_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 = nn_copy(&(crv->order), order); EG(ret, err);

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	crv->magic = EC_MONTGOMERY_CRV_MAGIC;

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err:

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	fp_uninit(&tmp);

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	return ret;

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}

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/* Uninitialize curve

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 */

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void ec_montgomery_crv_uninit(ec_montgomery_crv_t crv)

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{

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	if ((crv != NULL) && (crv->magic == EC_MONTGOMERY_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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