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.\"	$OpenBSD: RSA_blinding_on.3,v 1.7 2023/07/26 20:08:59 tb 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.
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.Dd $Mdocdate: July 26 2023 $
.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 .