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/*
* Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/* Internal EC functions for other submodules: not for application use */
#ifndef HEADER_OSSL_EC_INTERNAL_H
# define HEADER_OSSL_EC_INTERNAL_H
# include <openssl/opensslconf.h>
# ifndef OPENSSL_NO_EC
# include <openssl/ec.h>
/*
* Computes the multiplicative inverse of x in the range
* [1,EC_GROUP::order), where EC_GROUP::order is the cardinality of the
* subgroup generated by the generator G:
*
* res := x^(1) (mod EC_GROUP::order).
*
* This function expects the following two conditions to hold:
*  the EC_GROUP order is prime, and
*  x is included in the range [1, EC_GROUP::order).
*
* This function returns 1 on success, 0 on error.
*
* If the EC_GROUP order is even, this function explicitly returns 0 as
* an error.
* In case any of the two conditions stated above is not satisfied,
* the correctness of its output is not guaranteed, even if the return
* value could still be 1 (as primality testing and a conditional modular
* reduction round on the input can be omitted by the underlying
* implementations for better SCA properties on regular input values).
*/
__owur int ec_group_do_inverse_ord(const EC_GROUP *group, BIGNUM *res,
const BIGNUM *x, BN_CTX *ctx);
# endif /* OPENSSL_NO_EC */
#endif
