BN_COPY(3)                 Library Functions Manual                 BN_COPY(3)

NAME
     BN_copy, BN_dup, BN_with_flags - copy BIGNUMs

SYNOPSIS
     #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);

DESCRIPTION
     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 not
     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 can 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:

     o   dest should be a newly allocated BIGNUM obtained via a call to
         BN_new(3).  It should not have been used for other purposes or
         initialised in any way.

     o   dest must only be used in "read-only" operations, i.e. typically
         those functions where the relevant parameter is declared "const".

     o   dest must be used and freed before any further subsequent use of b.

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

SEE ALSO
     BN_new(3), BN_set_flags(3)

HISTORY
     BN_copy() and BN_dup() first appeared in SSLeay 0.5.1 and have been
     available since OpenBSD 2.4.

     BN_with_flags() first appeared in OpenSSL 0.9.7h and 0.9.8a and has been
     available since OpenBSD 4.0.

Linux 6.8.2-arch2-1            December 6, 2021            Linux 6.8.2-arch2-1