IABSD.fr/src/lib/libcrypto/ec/ec_internal.h

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• Author : jsing
  Date : 2025-08-02 15:44:09
  Hash : 12097217
  Message : Provide constant time conditional selection between EC_FIELD_ELEMENTs. Provide a ec_field_element_select() function that allows for constant time conditional selection between two EC_FIELD_ELEMENTs. This will become a building block for constant time point multiplication. ok tb@

• lib/libcrypto/ec/ec_internal.h

• /*	$OpenBSD: ec_internal.h,v 1.2 2025/08/02 15:44:09 jsing Exp $	*/
  /*
   * Copyright (c) 2024 Joel Sing <jsing@openbsd.org>
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <openssl/bn.h>
  
  #ifndef HEADER_EC_INTERNAL_H
  #define HEADER_EC_INTERNAL_H
  
  #define EC_FIELD_ELEMENT_MAX_BITS 521
  #define EC_FIELD_ELEMENT_MAX_BYTES \
      (EC_FIELD_ELEMENT_MAX_BITS + 7) / 8
  #define EC_FIELD_ELEMENT_MAX_WORDS \
      ((EC_FIELD_ELEMENT_MAX_BYTES + BN_BYTES - 1) / BN_BYTES)
  
  typedef struct {
  	BN_ULONG w[EC_FIELD_ELEMENT_MAX_WORDS];
  } EC_FIELD_ELEMENT;
  
  typedef struct {
  	size_t n;
  	EC_FIELD_ELEMENT m;
  	EC_FIELD_ELEMENT rr;
  	BN_ULONG minv0;
  } EC_FIELD_MODULUS;
  
  int ec_field_modulus_from_bn(EC_FIELD_MODULUS *fm, const BIGNUM *bn,
      BN_CTX *ctx);
  
  int ec_field_element_from_bn(const EC_FIELD_MODULUS *fm, const EC_GROUP *group,
      EC_FIELD_ELEMENT *fe, const BIGNUM *bn, BN_CTX *ctx);
  int ec_field_element_to_bn(const EC_FIELD_MODULUS *fm, const EC_FIELD_ELEMENT *fe,
      BIGNUM *bn, BN_CTX *ctx);
  
  void ec_field_element_copy(EC_FIELD_ELEMENT *dst, const EC_FIELD_ELEMENT *src);
  void ec_field_element_select(const EC_FIELD_MODULUS *fm, EC_FIELD_ELEMENT *r,
      const EC_FIELD_ELEMENT *a, const EC_FIELD_ELEMENT *b, int conditional);
  
  int ec_field_element_equal(const EC_FIELD_MODULUS *fm, const EC_FIELD_ELEMENT *a,
      const EC_FIELD_ELEMENT *b);
  int ec_field_element_is_zero(const EC_FIELD_MODULUS *fm, const EC_FIELD_ELEMENT *fe);
  
  void ec_field_element_add(const EC_FIELD_MODULUS *m, EC_FIELD_ELEMENT *r,
      const EC_FIELD_ELEMENT *a, const EC_FIELD_ELEMENT *b);
  void ec_field_element_sub(const EC_FIELD_MODULUS *m, EC_FIELD_ELEMENT *r,
      const EC_FIELD_ELEMENT *a, const EC_FIELD_ELEMENT *b);
  void ec_field_element_mul(const EC_FIELD_MODULUS *m, EC_FIELD_ELEMENT *r,
      const EC_FIELD_ELEMENT *a, const EC_FIELD_ELEMENT *b);
  void ec_field_element_sqr(const EC_FIELD_MODULUS *m, EC_FIELD_ELEMENT *r,
      const EC_FIELD_ELEMENT *a);
  
  #endif