DragonFly On-Line Manual Pages
RAND(3) LibreSSL RAND(3)
RAND - pseudo-random number generator
int RAND_bytes(unsigned char *buf, int num);
int RAND_pseudo_bytes(unsigned char *buf, int num);
These functions give access to the systems cryptographically secure
pseudo-random number generator (PRNG). It is used by other library
functions for example to generate random keys, and applications can use
it when they need randomness.
RAND_bytes(3) describes how to obtain random data from the PRNG.
The RAND_SSLeay() method implements a PRNG based on the systems'
arc4random_buf(3) random number generator.
LibreSSL 2017-01-09 RAND(3)
RAND_DRBG_GENERATE(3) OpenSSL RAND_DRBG_GENERATE(3)
RAND_DRBG_generate, RAND_DRBG_bytes - generate random bytes using the
given drbg instance
int RAND_DRBG_generate(RAND_DRBG *drbg,
unsigned char *out, size_t outlen,
const unsigned char *adin, size_t adinlen);
int RAND_DRBG_bytes(RAND_DRBG *drbg,
unsigned char *out, size_t outlen);
RAND_DRBG_generate() generates outlen random bytes using the given DRBG
instance drbg and stores them in the buffer at out.
Before generating the output, the DRBG instance checks whether the
maximum number of generate requests (reseed interval) or the maximum
timespan (reseed time interval) since its last seeding have been
reached. If this is the case, the DRBG reseeds automatically.
Additionally, an immediate reseeding can be requested by setting the
prediction_resistance flag to 1. See NOTES section for more details.
The caller can optionally provide additional data to be used for
reseeding by passing a pointer adin to a buffer of length adinlen.
This additional data is mixed into the internal state of the random
generator but does not contribute to the entropy count. The additional
data can be omitted by setting adin to NULL and adinlen to 0;
RAND_DRBG_bytes() generates outlen random bytes using the given DRBG
instance drbg and stores them in the buffer at out. This function is a
wrapper around the RAND_DRBG_generate() call, which collects some
additional data from low entropy sources (e.g., a high resolution
timer) and calls RAND_DRBG_generate(drbg, out, outlen, 0, adin,
RAND_DRBG_generate() and RAND_DRBG_bytes() return 1 on success, and 0
The reseed interval and reseed time interval of the drbg are set to
reasonable default values, which in general do not have to be adjusted.
If necessary, they can be changed using
A request for prediction resistance can only be satisfied by pulling
fresh entropy from one of the approved entropy sources listed in
section 5.5.2 of [NIST SP 800-90C]. Since the default DRBG
implementation does not have access to such an approved entropy source,
a request for prediction resistance will always fail. In other words,
prediction resistance is currently not supported yet by the DRBG.
The RAND_DRBG functions were added in OpenSSL 1.1.1.
Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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
1.1.1q 2022-07-05 RAND_DRBG_GENERATE(3)