focal (3) RAND_DRBG_bytes.3ssl.gz

Provided by: libssl-doc_1.1.1f-1ubuntu2.24_all bug

NAME
       RAND_DRBG_generate, RAND_DRBG_bytes - generate random bytes using the given drbg instance


SYNOPSIS
        #include <openssl/rand_drbg.h>

        int RAND_DRBG_generate(RAND_DRBG *drbg,
                               unsigned char *out, size_t outlen,
                               int prediction_resistance,
                               const unsigned char *adin, size_t adinlen);

        int RAND_DRBG_bytes(RAND_DRBG *drbg,
                            unsigned char *out, size_t outlen);


DESCRIPTION
       RAND_DRBG_generate() generates outlen random bytes using the given DRBG instance drbg and stores them in
       the buffer at out.

       Before generating the output, the DRBG instance checks whether the maximum number of generate requests
       (reseed interval) or the maximum timespan (reseed time interval) since its last seeding have been
       reached.  If this is the case, the DRBG reseeds automatically.  Additionally, an immediate reseeding can
       be requested by setting the prediction_resistance flag to 1. See NOTES section for more details.

       The caller can optionally provide additional data to be used for reseeding by passing a pointer adin to a
       buffer of length adinlen.  This additional data is mixed into the internal state of the random generator
       but does not contribute to the entropy count.  The additional data can be omitted by setting adin to NULL
       and adinlen to 0;

       RAND_DRBG_bytes() generates outlen random bytes using the given DRBG instance drbg and stores them in the
       buffer at out.  This function is a wrapper around the RAND_DRBG_generate() call, which collects some
       additional data from low entropy sources (e.g., a high resolution timer) and calls
       RAND_DRBG_generate(drbg, out, outlen, 0, adin, adinlen).


RETURN VALUES
       RAND_DRBG_generate() and RAND_DRBG_bytes() return 1 on success, and 0 on failure.


NOTES
       The reseed interval and reseed time interval of the drbg are set to reasonable default values, which in
       general do not have to be adjusted.  If necessary, they can be changed using
       RAND_DRBG_set_reseed_interval(3) and RAND_DRBG_set_reseed_time_interval(3), respectively.

       A request for prediction resistance can only be satisfied by pulling fresh entropy from one of the
       approved entropy sources listed in section 5.5.2 of [NIST SP 800-90C].  Since the default DRBG
       implementation does not have access to such an approved entropy source, a request for prediction
       resistance will always fail.  In other words, prediction resistance is currently not supported yet by the
       DRBG.


SEE ALSO
       RAND_bytes(3), RAND_DRBG_set_reseed_interval(3), RAND_DRBG_set_reseed_time_interval(3), RAND_DRBG(7)


HISTORY
       The RAND_DRBG functions were added in OpenSSL 1.1.1.


       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>.