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RAND_DRBG_reseed(3)                 OpenSSL                RAND_DRBG_reseed(3)



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

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/rand_drbg.h>

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

        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.  An immediate
       reseeding from a live entropy source can be requested by setting the
       prediction_resistance flag to 1.  This feature is not implemented yet,
       so reseeding with prediction resistance requested will always fail.

       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.

SEE ALSO
       RAND_DRBG_generate(3), RAND_DRBG_bytes(3), RAND_DRBG_set_callbacks(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>.



1.1.1i                            2019-06-09               RAND_DRBG_reseed(3)