RAND_GET0_PRIMARY(3ossl) OpenSSL RAND_GET0_PRIMARY(3ossl)
NAME
RAND_get0_primary, RAND_get0_public, RAND_get0_private,
RAND_set0_public, RAND_set0_private - get access to the global
EVP_RAND_CTX instances
SYNOPSIS
#include <openssl/rand.h>
EVP_RAND_CTX *RAND_get0_primary(OSSL_LIB_CTX *ctx);
EVP_RAND_CTX *RAND_get0_public(OSSL_LIB_CTX *ctx);
EVP_RAND_CTX *RAND_get0_private(OSSL_LIB_CTX *ctx);
int RAND_set0_public(OSSL_LIB_CTX *ctx, EVP_RAND_CTX *rand);
int RAND_set0_private(OSSL_LIB_CTX *ctx, EVP_RAND_CTX *rand);
DESCRIPTION
The default RAND API implementation (RAND_OpenSSL()) utilizes three
shared DRBG instances which are accessed via the RAND API:
The public and private DRBG are thread-local instances, which are used
by RAND_bytes() and RAND_priv_bytes(), respectively. The primary DRBG
is a global instance, which is not intended to be used directly, but is
used internally to reseed the other two instances.
The three get functions provide access to the shared DRBG instances.
The two set functions allow the public and private DRBG instances to be
replaced by another random number generator.
RETURN VALUES
RAND_get0_primary(3) returns a pointer to the primary DRBG instance for
the given OSSL_LIB_CTX ctx.
RAND_get0_public() returns a pointer to the public DRBG instance for
the given OSSL_LIB_CTX ctx.
RAND_get0_private() returns a pointer to the private DRBG instance for
the given OSSL_LIB_CTX ctx.
RAND_set0_public() and RAND_set0_private() return 1 on success and 0 on
error.
NOTES
It is not thread-safe to access the primary DRBG instance. The public
and private DRBG instance can be accessed safely, because they are
thread-local. Note however, that changes to these two instances apply
only to the current thread.
For that reason it is recommended not to change the settings of these
three instances directly. Instead, an application should change the
default settings for new DRBG instances at initialization time, before
creating additional threads.
During initialization, it is possible to change the reseed interval and
reseed time interval. It is also possible to exchange the reseeding
callbacks entirely.
To set the type of DRBG that will be instantiated, use the
RAND_set_DRBG_type(3) call before accessing the random number
generation infrastructure.
The two set functions, operate on the current thread. If you want to
use the same random number generator across all threads, each thread
must individually call the set functions.
SEE ALSO
EVP_RAND(3), RAND_set_DRBG_type(3)
HISTORY
RAND_set0_public() and RAND_set0_private() were added in OpenSSL 3.1.
The remaining functions were added in OpenSSL 3.0.
COPYRIGHT
Copyright 2020-2024 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>.
3.5.0 2025-04-10 RAND_GET0_PRIMARY(3ossl)
openssl 3.5.0 - Generated Sat Apr 26 15:56:08 CDT 2025