BN_COPY(3ssl) OpenSSL BN_COPY(3ssl)

BN_copy, BN_dup, BN_with_flags - copy BIGNUMs

#include <openssl/bn.h>
BIGNUM *BN_copy(BIGNUM *to, const BIGNUM *from);
BIGNUM *BN_dup(const BIGNUM *from);
void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags);

BN_copy() copies from to to. BN_dup() creates a new BIGNUM containing the value from.

BN_with_flags creates a temporary shallow copy of b in dest. It places significant restrictions on the copied data. Applications that do no adhere to these restrictions may encounter unexpected side effects or crashes. For that reason use of this function is discouraged. Any flags provided in flags will be set in dest in addition to any flags already set in b. For example this might commonly be used to create a temporary copy of a BIGNUM with the BN_FLG_CONSTTIME flag set for constant time operations. The temporary copy in dest will share some internal state with b. For this reason the following restrictions apply to the use of dest:

  • dest should be a newly allocated BIGNUM obtained via a call to BN_new(). It should not have been used for other purposes or initialised in any way.
  • dest must only be used in "read-only" operations, i.e. typically those functions where the relevant parameter is declared "const".
  • dest must be used and freed before any further subsequent use of b

BN_copy() returns to on success, NULL on error. BN_dup() returns the new BIGNUM, and NULL on error. The error codes can be obtained by ERR_get_error(3).


Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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

2024-06-04 3.3.1