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Title "RAND_EGD 3"
RAND_EGD 3 "2023-08-01" "3.0.10" "OpenSSL"
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"NAME"
RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes - query entropy gathering daemon
"SYNOPSIS"
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
"DESCRIPTION"
Header "DESCRIPTION" On older platforms without a good source of randomness such as \*(C`/dev/urandom\*(C', 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>.

\fBRAND_egd_bytes() requests num bytes of randomness from an \s-1EGD\s0 at the specified socket path, and passes the data it receives into RAND_add(). \fBRAND_egd() is equivalent to RAND_egd_bytes() with num set to 255.

\fBRAND_query_egd_bytes() requests num bytes of randomness from an \s-1EGD\s0 at the specified socket path, where num must be less than 256. If buf is \s-1NULL\s0, it is equivalent to RAND_egd_bytes(). If buf is not \s-1NULL\s0, then the data is copied to the buffer and \fBRAND_add() is not called.

OpenSSL can be configured at build time to try to use the \s-1EGD\s0 for seeding automatically.

"RETURN VALUES"
Header "RETURN VALUES" \fBRAND_egd() and RAND_egd_bytes() 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

\fBRAND_query_egd_bytes() returns the number of bytes read from the daemon on success, or -1 if the connection failed.

"SEE ALSO"
Header "SEE ALSO" \fBRAND_add\|(3), \fBRAND_bytes\|(3), \s-1RAND\s0\|(7)
"COPYRIGHT"
Header "COPYRIGHT" Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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>.