.\"	$NetBSD: RAND_set_rand_method.3,v 1.6 2002/02/07 07:00:39 ross Exp $
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.\"
.IX Title "RAND_set_rand_method 3"
.TH RAND_set_rand_method 3 "0.9.6a" "2000-07-22" "OpenSSL"
.UC
.SH "NAME"
RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay \- select \s-1RAND\s0 method
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include \*[Lt]openssl/rand.h\*[Gt]
.Ve
.Vb 1
\& void RAND_set_rand_method(RAND_METHOD *meth);
.Ve
.Vb 1
\& RAND_METHOD *RAND_get_rand_method(void);
.Ve
.Vb 1
\& RAND_METHOD *RAND_SSLeay(void);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A \fB\s-1RAND_METHOD\s0\fR specifies the functions that OpenSSL uses for random
number generation. By modifying the method, alternative
implementations such as hardware RNGs may be used.  Initially, the
default is to use the OpenSSL internal implementation. \fIRAND_SSLeay()\fR
returns a pointer to that method.
.PP
\&\fIRAND_set_rand_method()\fR sets the \s-1RAND\s0 method to \fBmeth\fR.
\&\fIRAND_get_rand_method()\fR returns a pointer to the current method.
.SH "THE RAND_METHOD STRUCTURE"
.IX Header "THE RAND_METHOD STRUCTURE"
.Vb 9
\& typedef struct rand_meth_st
\& {
\&        void (*seed)(const void *buf, int num);
\&        int (*bytes)(unsigned char *buf, int num);
\&        void (*cleanup)(void);
\&        void (*add)(const void *buf, int num, int entropy);
\&        int (*pseudorand)(unsigned char *buf, int num);
\&        int (*status)(void);
\& } RAND_METHOD;
.Ve
The components point to the implementation of \fIRAND_seed()\fR,
\&\fIRAND_bytes()\fR, \fIRAND_cleanup()\fR, \fIRAND_add()\fR, \fIRAND_pseudo_rand()\fR
and \fIRAND_status()\fR.
Each component may be \s-1NULL\s0 if the function is not implemented.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIRAND_set_rand_method()\fR returns no value. \fIRAND_get_rand_method()\fR and
\&\fIRAND_SSLeay()\fR return pointers to the respective methods.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
openssl_rand(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fIRAND_set_rand_method()\fR, \fIRAND_get_rand_method()\fR and \fIRAND_SSLeay()\fR are
available in all versions of OpenSSL.