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.\" ========================================================================
.\"
.IX Title "RAND_EGD 3"
.TH RAND_EGD 3 "2023-09-11" "1.1.1w" "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_egd, RAND_egd_bytes, RAND_query_egd_bytes \- query entropy gathering daemon
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/rand.h>
\&
\& int RAND_egd_bytes(const char *path, int num);
\& int RAND_egd(const char *path);
\&
\& int RAND_query_egd_bytes(const char *path, unsigned char *buf, int num);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
On older platforms without a good source of randomness such as \f(CW\*(C`/dev/urandom\*(C'\fR,
it is possible to query an Entropy Gathering Daemon (\s-1EGD\s0) over a local
socket to obtain randomness and seed the OpenSSL \s-1RNG.\s0
The protocol used is defined by the EGDs available at
<http://egd.sourceforge.net/> or <http://prngd.sourceforge.net>.
.PP
\&\fBRAND_egd_bytes()\fR requests \fBnum\fR bytes of randomness from an \s-1EGD\s0 at the
specified socket \fBpath\fR, and passes the data it receives into \fBRAND_add()\fR.
\&\fBRAND_egd()\fR is equivalent to \fBRAND_egd_bytes()\fR with \fBnum\fR set to 255.
.PP
\&\fBRAND_query_egd_bytes()\fR requests \fBnum\fR bytes of randomness from an \s-1EGD\s0 at
the specified socket \fBpath\fR, where \fBnum\fR must be less than 256.
If \fBbuf\fR is \fB\s-1NULL\s0\fR, it is equivalent to \fBRAND_egd_bytes()\fR.
If \fBbuf\fR is not \fB\s-1NULL\s0\fR, then the data is copied to the buffer and
\&\fBRAND_add()\fR is not called.
.PP
OpenSSL can be configured at build time to try to use the \s-1EGD\s0 for seeding
automatically.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBRAND_egd()\fR and \fBRAND_egd_bytes()\fR return the number of bytes read from the
daemon on success, or \-1 if the connection failed or the daemon did not
return enough data to fully seed the \s-1PRNG.\s0
.PP
\&\fBRAND_query_egd_bytes()\fR returns the number of bytes read from the daemon on
success, or \-1 if the connection failed.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBRAND_add\fR\|(3),
\&\fBRAND_bytes\fR\|(3),
\&\s-1\fBRAND\s0\fR\|(7)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2018 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>.