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.\" ========================================================================
.\"
.IX Title "RAND_set_rand_method 3"
.TH RAND_set_rand_method 3 "2020-04-24" "1.1.1i" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL \- select RAND method
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rand.h>
\&
\& RAND_METHOD *RAND_OpenSSL(void);
\&
\& int RAND_set_rand_method(const RAND_METHOD *meth);
\&
\& const RAND_METHOD *RAND_get_rand_method(void);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A \fB\s-1RAND_METHOD\s0\fR specifies the functions that OpenSSL uses for random number
generation.
.PP
\&\fBRAND_OpenSSL()\fR returns the default \fB\s-1RAND_METHOD\s0\fR implementation by OpenSSL.
This implementation ensures that the \s-1PRNG\s0 state is unique for each thread.
.PP
If an \fB\s-1ENGINE\s0\fR is loaded that provides the \s-1RAND API,\s0 however, it will
be used instead of the method returned by \fBRAND_OpenSSL()\fR.
.PP
\&\fBRAND_set_rand_method()\fR makes \fBmeth\fR the method for \s-1PRNG\s0 use.  If an
\&\s-1ENGINE\s0 was providing the method, it will be released first.
.PP
\&\fBRAND_get_rand_method()\fR returns a pointer to the current \fB\s-1RAND_METHOD\s0\fR.
.SH "THE RAND_METHOD STRUCTURE"
.IX Header "THE RAND_METHOD STRUCTURE"
.Vb 8
\& typedef struct rand_meth_st {
\&     int (*seed)(const void *buf, int num);
\&     int (*bytes)(unsigned char *buf, int num);
\&     void (*cleanup)(void);
\&     int (*add)(const void *buf, int num, double entropy);
\&     int (*pseudorand)(unsigned char *buf, int num);
\&     int (*status)(void);
\& } RAND_METHOD;
.Ve
.PP
The fields point to functions that are used by, in order,
\&\fBRAND_seed()\fR, \fBRAND_bytes()\fR, internal \s-1RAND\s0 cleanup, \fBRAND_add()\fR, \fBRAND_pseudo_rand()\fR
and \fBRAND_status()\fR.
Each pointer may be \s-1NULL\s0 if the function is not implemented.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBRAND_set_rand_method()\fR returns 1 on success and 0 on failure.
\&\fBRAND_get_rand_method()\fR and \fBRAND_OpenSSL()\fR return pointers to the respective
methods.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBRAND_bytes\fR\|(3),
\&\fBENGINE_by_id\fR\|(3),
\&\s-1\fBRAND\s0\fR\|(7)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.