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.IX Title "BN_MOD_INVERSE 3ssl"
.TH BN_MOD_INVERSE 3ssl 2024-10-23 3.4.0 OpenSSL
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH NAME
BN_mod_inverse \- compute inverse modulo n
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bn.h>
\&
\& BIGNUM *BN_mod_inverse(BIGNUM *r, BIGNUM *a, const BIGNUM *n,
\&                        BN_CTX *ctx);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBBN_mod_inverse()\fR computes the inverse of \fBa\fR modulo \fBn\fR
places the result in \fBr\fR (\f(CW\*(C`(a*r)%n==1\*(C'\fR). If \fBr\fR is NULL,
a new \fBBIGNUM\fR is created.
.PP
\&\fBctx\fR is a previously allocated \fBBN_CTX\fR used for temporary
variables. \fBr\fR may be the same \fBBIGNUM\fR as \fBa\fR.
.SH NOTES
.IX Header "NOTES"
It is an error to use the same \fBBIGNUM\fR as \fBn\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBN_mod_inverse()\fR returns the \fBBIGNUM\fR containing the inverse, and
NULL on error. The error codes can be obtained by \fBERR_get_error\fR\|(3).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBERR_get_error\fR\|(3), \fBBN_add\fR\|(3)
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2000\-2017 The OpenSSL Project Authors. All Rights Reserved.
.PP
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
<https://www.openssl.org/source/license.html>.