RAND_add, RAND_poll, RAND_seed, RAND_status, RAND_event, RAND_screen,
RAND_keep_random_devices_open - add randomness to the PRNG or get its status
#include <openssl/rand.h>
int RAND_status(void);
int RAND_poll();
void RAND_add(const void *buf, int num, double randomness);
void RAND_seed(const void *buf, int num);
void RAND_keep_random_devices_open(int keep);
The following functions have been deprecated since OpenSSL 1.1.0, and can be
hidden entirely by defining
OPENSSL_API_COMPAT with a suitable version
value, see
openssl_user_macros(7):
int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
void RAND_screen(void);
These functions can be used to seed the random generator and to check its seeded
state. In general, manual (re-)seeding of the default OpenSSL random generator
(
RAND_OpenSSL(3)) is not necessary (but allowed), since it does
(re-)seed itself automatically using trusted system entropy sources. This
holds unless the default RAND_METHOD has been replaced or OpenSSL was built
with automatic reseeding disabled, see
RAND(7) for more details.
RAND_status() indicates whether or not the random generator has been
sufficiently seeded. If not, functions such as
RAND_bytes(3) will fail.
RAND_poll() uses the system's capabilities to seed the random generator
using random input obtained from polling various trusted entropy sources. The
default choice of the entropy source can be modified at build time, see
RAND(7) for more details.
RAND_add() mixes the
num bytes at
buf into the internal
state of the random generator. This function will not normally be needed, as
mentioned above. The
randomness argument is an estimate of how much
randomness is contained in
buf, in bytes, and should be a number
between zero and
num. Details about sources of randomness and how to
estimate their randomness can be found in the literature; for example [NIST SP
800-90B]. The content of
buf cannot be recovered from subsequent random
generator output. Applications that intend to save and restore random state in
an external file should consider using
RAND_load_file(3) instead.
NOTE: In FIPS mode, random data provided by the application is not considered to
be a trusted entropy source. It is mixed into the internal state of the RNG as
additional data only and this does not count as a full reseed. For more
details, see
EVP_RAND(7).
RAND_seed() is equivalent to
RAND_add() with
randomness set
to
num.
RAND_keep_random_devices_open() is used to control file descriptor usage
by the random seed sources. Some seed sources maintain open file descriptors
by default, which allows such sources to operate in a
chroot(2) jail
without the associated device nodes being available. When the
keep
argument is zero, this call disables the retention of file descriptors.
Conversely, a nonzero argument enables the retention of file descriptors. This
function is usually called during initialization and it takes effect
immediately. This capability only applies to the default provider.
RAND_event() and
RAND_screen() are equivalent to
RAND_poll() and exist for compatibility reasons only. See HISTORY
section below.
RAND_status() returns 1 if the random generator has been seeded with
enough data, 0 otherwise.
RAND_poll() returns 1 if it generated seed data, 0 otherwise.
RAND_event() returns
RAND_status().
The other functions do not return values.
RAND_bytes(3),
RAND_egd(3),
RAND_load_file(3),
RAND(7) EVP_RAND(7)
RAND_event() and
RAND_screen() were deprecated in OpenSSL 1.1.0
and should not be used.
Copyright 2000-2021 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>.