.\"	$OpenBSD: RSA_blinding_on.3,v 1.2 2016/11/06 15:52:50 jmc Exp $
.\"
.Dd $Mdocdate: November 6 2016 $
.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 3
.Sh HISTORY
.Fn RSA_blinding_on
and
.Fn RSA_blinding_off
appeared in SSLeay 0.9.0.