---
name: "RAND_DRBG_get0_master"
section: "3ssl"
platform: "linux"
package: "libssl-doc"
version: "1.1.1w-0+deb11u1"
release: "Debian 11 (Bullseye)"
platforms: ["linux"]
url: "https://new.carta.tech/RAND_DRBG_get0_master"
---

# RAND\_DRBG\_get0\_master(3ssl)

get access to the global RAND\_DRBG instances

## NAME

RAND\_DRBG\_get0\_master, RAND\_DRBG\_get0\_public, RAND\_DRBG\_get0\_private - get access to the global RAND\_DRBG instances

## SYNOPSIS

```
 #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);
```

## 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 \<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.

## NOTES

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)

## HISTORY

The RAND\_DRBG functions were added in OpenSSL 1.1.1.

## COPYRIGHT

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 \<https://www.openssl.org/source/license.html\>.