RAND_EGD(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

💜 RAND_EGD 💜

okay so this is the RAND_EGD(3ossl) page from the OpenSSL fam — yes bestie, the 3ossl part is the manual section, we love a labeled moment ✨

🌸 NAME 🌸

RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes — the trio that goes and asks an entropy gathering daemon for some randomness, fr fr 🎀

⭐ SYNOPSIS ⭐

#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);

three little functions, one big vibe check on your randomness situation 💅

🦋 DESCRIPTION 🦋

So picture this: you're on an older platform that doesn't have a good source of randomness — like, no "/dev/urandom" to be found 😭 — and you still need to seed the OpenSSL RNG. The move? Query an Entropy Gathering Daemon (EGD) over a local socket and borrow some randomness from it. iconic behavior honestly 👑

The protocol in play is defined by the EGDs you can find at <http://egd.sourceforge.net/> or <http://prngd.sourceforge.net>. iykyk 🌈

  • RAND_egd_bytes() — asks for num bytes of randomness from an EGD sitting at the socket path you specify, then takes the data it gets back and hands it straight to RAND_add(). chef's kiss 🍓
  • RAND_egd() — literally the same thing as RAND_egd_bytes() except num is set to 255. that's it, that's the whole difference 💀
  • RAND_query_egd_bytes() — asks for num bytes of randomness from the EGD at path, and heads up: num must be less than 256. If buf is NULL, it's equivalent to RAND_egd_bytes(). But if buf is not NULL, the data gets copied into that buffer instead and RAND_add() is not called. choose your fighter 🫶

Also, fun fact: OpenSSL can be configured at build time to try to use the EGD for seeding automatically. convenient much? ✨

🔥 RETURN VALUES 🔥

  • RAND_egd() and RAND_egd_bytes() — on success they return the number of bytes read from the daemon 💖 but if the connection failed, or the daemon didn't return enough data to fully seed the PRNG, you get -1. sad girl hours 😭
  • RAND_query_egd_bytes() — returns the number of bytes read from the daemon on success, or -1 if the connection failed. no fully-seeded-PRNG drama here, just connection vibes 💅

🌟 SEE ALSO 🌟

RAND_add(3), RAND_bytes(3), RAND(7) — go read these next, bestie, they're the main characters of this friend group 👑

Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved. 🫶

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>. read the license, it's giving responsible queen behavior 💜

and that's the whole page, bestie! this one's from OpenSSL 3.5.0, dated 2026-09-25 — slay, go seed something responsibly 🌈✨💖

📦 where this page comes from