Updated: 2022/Sep/29

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RAND_egd(3)                         OpenSSL                        RAND_egd(3)



NAME
       RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes - query entropy
       gathering daemon

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/rand.h>

        int RAND_egd_bytes(const char *path, int num);
        int RAND_egd(const char *path);

        int RAND_query_egd_bytes(const char *path, unsigned char *buf, int num);

DESCRIPTION
       On older platforms without a good source of randomness such as
       "/dev/urandom", it is possible to query an Entropy Gathering Daemon
       (EGD) over a local socket to obtain randomness and seed the OpenSSL
       RNG. The protocol used is defined by the EGDs available at
       <http://egd.sourceforge.net/> or <http://prngd.sourceforge.net>.

       RAND_egd_bytes() requests num bytes of randomness from an EGD at the
       specified socket path, and passes the data it receives into RAND_add().
       RAND_egd() is equivalent to RAND_egd_bytes() with num set to 255.

       RAND_query_egd_bytes() requests num bytes of randomness from an EGD at
       the specified socket path, where num must be less than 256.  If buf is
       NULL, it is equivalent to RAND_egd_bytes().  If buf is not NULL, then
       the data is copied to the buffer and RAND_add() is not called.

       OpenSSL can be configured at build time to try to use the EGD for
       seeding automatically.

RETURN VALUES
       RAND_egd() and RAND_egd_bytes() return the number of bytes read from
       the daemon on success, or -1 if the connection failed or the daemon did
       not return enough data to fully seed the PRNG.

       RAND_query_egd_bytes() returns the number of bytes read from the daemon
       on success, or -1 if the connection failed.

SEE ALSO
       RAND_add(3), RAND_bytes(3), RAND(7)

COPYRIGHT
       Copyright 2000-2018 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>.



3.0.12                            2023-05-07                       RAND_egd(3)