huschi.net

RAND_ADD(3)                         OpenSSL                        RAND_ADD(3)
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);
       Deprecated:
        #if OPENSSL_API_COMPAT < 0x10100000L
        int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
        void RAND_screen(void);
        #endif
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.
       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.
       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)
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 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>;.
1.1.1k                            2021-03-25                       RAND_ADD(3)