RAND_DRBG_get0_master.3ssl - Man Page

get access to the global RAND_DRBG instances


 #include <openssl/rand_drbg.h>

 RAND_DRBG *RAND_DRBG_get0_master(void);
 RAND_DRBG *RAND_DRBG_get0_public(void);
 RAND_DRBG *RAND_DRBG_get0_private(void);


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 <master> DRBG is a global instance, which is not intended to be used directly, but is used internally to reseed the other two instances.

These functions here provide access to the shared DRBG instances.

Return Values

RAND_DRBG_get0_master() returns a pointer to the <master> DRBG instance.

RAND_DRBG_get0_public() returns a pointer to the <public> DRBG instance.

RAND_DRBG_get0_private() returns a pointer to the <private> DRBG instance.


It is not thread-safe to access the <master> 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.

See Also

RAND_DRBG_set_callbacks(3), RAND_DRBG_set_reseed_defaults(3), RAND_DRBG_set_reseed_interval(3), RAND_DRBG_set_reseed_time_interval(3), RAND_DRBG_set_callbacks(3), RAND_DRBG_generate(3), RAND_DRBG(7)


The RAND_DRBG functions were added in OpenSSL 1.1.1.

Referenced By

The man pages RAND_DRBG_get0_private.3ssl(3) and RAND_DRBG_get0_public.3ssl(3) are aliases of RAND_DRBG_get0_master.3ssl(3).

2023-01-19 1.1.1q OpenSSL