1.\" $OpenBSD: RSA_blinding_on.3,v 1.7 2023/07/26 20:08:59 tb Exp $ 2.\" OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400 3.\" 4.\" This file was written by Ulf Moeller <ulf@openssl.org>. 5.\" Copyright (c) 2000 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: July 26 2023 $ 52.Dt RSA_BLINDING_ON 3 53.Os 54.Sh NAME 55.Nm RSA_blinding_on , 56.Nm RSA_blinding_off 57.Nd protect the RSA operation from timing attacks 58.Sh SYNOPSIS 59.In openssl/rsa.h 60.Ft int 61.Fo RSA_blinding_on 62.Fa "RSA *rsa" 63.Fa "BN_CTX *ctx" 64.Fc 65.Ft void 66.Fo RSA_blinding_off 67.Fa "RSA *rsa" 68.Fc 69.Sh DESCRIPTION 70RSA is vulnerable to timing attacks. 71In a setup where attackers can measure the time of RSA decryption or 72signature operations, blinding must be used to protect the RSA operation 73from that attack. 74.Pp 75.Fn RSA_blinding_on 76turns blinding on for key 77.Fa rsa 78and generates a random blinding factor. 79.Fa ctx 80is 81.Dv NULL 82or a pre-allocated and initialized 83.Vt BN_CTX . 84.Pp 85.Fn RSA_blinding_off 86turns blinding off and frees the memory used for the blinding factor. 87.Sh RETURN VALUES 88.Fn RSA_blinding_on 89returns 1 on success, and 0 if an error occurred. 90.Sh SEE ALSO 91.Xr RSA_new 3 92.Sh HISTORY 93.Fn RSA_blinding_on 94and 95.Fn RSA_blinding_off 96first appeared in SSLeay 0.9.0 and have been available since 97.Ox 2.4 . 98