NAME

       RAND_DRBG_reseed, RAND_DRBG_set_reseed_interval, RAND_DRBG_set_reseed_time_interval,
       RAND_DRBG_set_reseed_defaults - reseed a RAND_DRBG instance

SYNOPSIS

        #include <openssl/rand_drbg.h>

        int RAND_DRBG_reseed(RAND_DRBG *drbg,
                             const unsigned char *adin, size_t adinlen);

        int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg,
                                          unsigned int interval);

        int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg,
                                               time_t interval);

        int RAND_DRBG_set_reseed_defaults(
                                          unsigned int master_reseed_interval,
                                          unsigned int slave_reseed_interval,
                                          time_t master_reseed_time_interval,
                                          time_t slave_reseed_time_interval
                                          );

DESCRIPTION

       RAND_DRBG_reseed() reseeds the given drbg, obtaining entropy input from its entropy source and mixing in
       the specified additional data provided in the buffer adin of length adinlen.  The additional data can be
       omitted by setting adin to NULL and adinlen to 0.

       RAND_DRBG_set_reseed_interval() sets the reseed interval of the drbg, which is the maximum allowed number
       of generate requests between consecutive reseedings.  If interval > 0, then the drbg will reseed
       automatically whenever the number of generate requests since its last seeding exceeds the given reseed
       interval.  If interval == 0, then this feature is disabled.

       RAND_DRBG_set_reseed_time_interval() sets the reseed time interval of the drbg, which is the maximum
       allowed number of seconds between consecutive reseedings.  If interval > 0, then the drbg will reseed
       automatically whenever the elapsed time since its last reseeding exceeds the given reseed time interval.
       If interval == 0, then this feature is disabled.

       RAND_DRBG_set_reseed_defaults() sets the default values for the reseed interval (master_reseed_interval
       and slave_reseed_interval) and the reseed time interval (master_reseed_time_interval and
       slave_reseed_tme_interval) of DRBG instances.  The default values are set independently for master DRBG
       instances (which don't have a parent) and slave DRBG instances (which are chained to a parent DRBG).

RETURN VALUES

       RAND_DRBG_reseed(), RAND_DRBG_set_reseed_interval(), and RAND_DRBG_set_reseed_time_interval(), return 1
       on success, 0 on failure.

NOTES

       The default OpenSSL random generator is already set up for automatic reseeding, so in general it is not
       necessary to reseed it explicitly, or to modify its reseeding thresholds.

       Normally, the entropy input for seeding a DRBG is either obtained from a trusted os entropy source or
       from a parent DRBG instance, which was seeded (directly or indirectly) from a trusted os entropy source.
       In exceptional cases it is possible to replace the reseeding mechanism entirely by providing application
       defined callbacks using RAND_DRBG_set_callbacks().

       The reseeding default values are applied only during creation of a DRBG instance.  To ensure that they
       are applied to the global and thread-local DRBG instances (<master>, resp. <public> and <private>), it is
       necessary to call RAND_DRBG_set_reseed_defaults() before creating any thread and before calling any
        cryptographic routines that obtain random data directly or indirectly.

HISTORY

       The RAND_DRBG functions were added in OpenSSL 1.1.1.

SEE ALSO

       RAND_DRBG_generate(3), RAND_DRBG_bytes(3), RAND_DRBG_set_callbacks(3).  RAND_DRBG(7)

COPYRIGHT

       Copyright 2017-2018 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>.