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.\" ========================================================================
.\"
.IX Title "BN_NEW 3ossl"
.TH BN_NEW 3ossl "2026-01-16" "3.5.1" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
BN_new, BN_secure_new, BN_clear, BN_free, BN_clear_free \- allocate and free BIGNUMs
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bn.h>
\&
\& BIGNUM *BN_new(void);
\&
\& BIGNUM *BN_secure_new(void);
\&
\& void BN_clear(BIGNUM *a);
\&
\& void BN_free(BIGNUM *a);
\&
\& void BN_clear_free(BIGNUM *a);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBBN_new()\fR allocates and initializes a \fB\s-1BIGNUM\s0\fR structure.
\&\fBBN_secure_new()\fR does the same except that the secure heap
\&\fBOPENSSL_secure_malloc\fR\|(3) is used to store the value.
.PP
\&\fBBN_clear()\fR is used to destroy sensitive data such as keys when they
are no longer needed. It erases the memory used by \fBa\fR and sets it
to the value 0.
If \fBa\fR is \s-1NULL,\s0 nothing is done.
.PP
\&\fBBN_free()\fR frees the components of the \fB\s-1BIGNUM\s0\fR, and if it was created
by \fBBN_new()\fR, also the structure itself. \fBBN_clear_free()\fR additionally
overwrites the data before the memory is returned to the system.
If \fBa\fR is \s-1NULL,\s0 nothing is done.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBN_new()\fR and \fBBN_secure_new()\fR
return a pointer to the \fB\s-1BIGNUM\s0\fR initialised to the value 0.
If the allocation fails,
they return \fB\s-1NULL\s0\fR and set an error code that can be obtained
by \fBERR_get_error\fR\|(3).
.PP
\&\fBBN_clear()\fR, \fBBN_free()\fR and \fBBN_clear_free()\fR have no return values.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBERR_get_error\fR\|(3), \fBOPENSSL_secure_malloc\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBBN_init()\fR was removed in OpenSSL 1.1.0; use \fBBN_new()\fR instead.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2017 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
