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.IX Title "RSA_BLINDING_ON 3ssl"
.TH RSA_BLINDING_ON 3ssl 2024-10-23 3.4.0 OpenSSL
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.SH NAME
RSA_blinding_on, RSA_blinding_off \- protect the RSA operation from timing attacks
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rsa.h>
.Ve
.PP
The following functions have been deprecated since OpenSSL 3.0, and can be
hidden entirely by defining \fBOPENSSL_API_COMPAT\fR with a suitable version value,
see \fBopenssl_user_macros\fR\|(7):
.PP
.Vb 1
\& int RSA_blinding_on(RSA *rsa, BN_CTX *ctx);
\&
\& void RSA_blinding_off(RSA *rsa);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
All of the functions described on this page are deprecated.
.PP
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
\&\fBRSA_blinding_on()\fR turns blinding on for key \fBrsa\fR and generates a
random blinding factor. \fBctx\fR is \fBNULL\fR or a preallocated and
initialized \fBBN_CTX\fR.
.PP
\&\fBRSA_blinding_off()\fR turns blinding off and frees the memory used for
the blinding factor.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBRSA_blinding_on()\fR returns 1 on success, and 0 if an error occurred.
.PP
\&\fBRSA_blinding_off()\fR returns no value.
.SH HISTORY
.IX Header "HISTORY"
All of these functions were deprecated in OpenSSL 3.0.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2000\-2021 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>.