.\"	$OpenBSD: RSA_blinding_on.3,v 1.5 2018/03/21 07:25:59 schwarze Exp $
.\"	OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000 The OpenSSL Project.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in
.\"    the documentation and/or other materials provided with the
.\"    distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\"    software must display the following acknowledgment:
.\"    "This product includes software developed by the OpenSSL Project
.\"    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\"    endorse or promote products derived from this software without
.\"    prior written permission. For written permission, please contact
.\"    openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\"    nor may "OpenSSL" appear in their names without prior written
.\"    permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\"    acknowledgment:
.\"    "This product includes software developed by the OpenSSL Project
.\"    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: March 21 2018 $
.Dt RSA_BLINDING_ON 3
.Os
.Sh NAME
.Nm RSA_blinding_on ,
.Nm RSA_blinding_off
.Nd protect the RSA operation from timing attacks
.Sh SYNOPSIS
.In openssl/rsa.h
.Ft int
.Fo RSA_blinding_on
.Fa "RSA *rsa"
.Fa "BN_CTX *ctx"
.Fc
.Ft void
.Fo RSA_blinding_off
.Fa "RSA *rsa"
.Fc
.Sh DESCRIPTION
RSA is vulnerable to timing attacks.
In a setup where attackers can measure the time of RSA decryption or
signature operations, blinding must be used to protect the RSA operation
from that attack.
.Pp
.Fn RSA_blinding_on
turns blinding on for key
.Fa rsa
and generates a random blinding factor.
.Fa ctx
is
.Dv NULL
or a pre-allocated and initialized
.Vt BN_CTX .
.Pp
.Fn RSA_blinding_off
turns blinding off and frees the memory used for the blinding factor.
.Sh RETURN VALUES
.Fn RSA_blinding_on
returns 1 on success, and 0 if an error occurred.
.Sh SEE ALSO
.Xr RSA_new 3
.Sh HISTORY
.Fn RSA_blinding_on
and
.Fn RSA_blinding_off
first appeared in SSLeay 0.9.0 and have been available since
.Ox 2.4 .