RAND_ADD(3ossl) OpenSSL RAND_ADD(3ossl)
NAME
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
SYNOPSIS
#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);
DESCRIPTION
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(3) 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_add(3) 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.
RETURN VALUES
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.
SEE ALSO
RAND_bytes(3), RAND_egd(3), RAND_load_file(3), RAND(7) EVP_RAND(7)
HISTORY
RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and
should not be used.
COPYRIGHT
Copyright 2000-2020 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>.
3.3.2 2024-09-04 RAND_ADD(3ossl)
openssl 3.3.2 - Generated Thu Sep 19 16:06:48 CDT 2024