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() 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.

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 2000-2021 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>.