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.\" ========================================================================
.\"
.IX Title "RSA_blinding_on 3"
.TH RSA_blinding_on 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.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>
\&
\& int RSA_blinding_on(RSA *rsa, BN_CTX *ctx);
\&
\& void RSA_blinding_off(RSA *rsa);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1RSA\s0 is vulnerable to timing attacks. In a setup where attackers can
measure the time of \s-1RSA\s0 decryption or signature operations, blinding
must be used to protect the \s-1RSA\s0 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 \fB\s-1NULL\s0\fR or a pre-allocated and
initialized \fB\s-1BN_CTX\s0\fR. The random number generator must be seeded
prior to calling \fBRSA_blinding_on()\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 "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBrsa\fR\|(3), \fBrand\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBRSA_blinding_on()\fR and \fBRSA_blinding_off()\fR appeared in SSLeay 0.9.0.