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NAME

     RAND_egd - query entropy gathering daemon



SYNOPSIS
      #include <openssl/rand.h>

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




DESCRIPTION
     RAND_egd() queries the entropy gathering daemon EGD on
     socket path.  It queries 255 bytes and uses RAND_add(3) to
     seed the OpenSSL built-in PRNG. RAND_egd(path) is a wrapper
     for RAND_egd_bytes(path, 255);

     RAND_egd_bytes() queries the entropy gathering daemon EGD on
     socket path.  It queries bytes bytes and uses RAND_add(3) to
     seed the OpenSSL built-in PRNG.  This function is more
     flexible than RAND_egd().  When only one secret key must be
     generated, it is not necessary to request the full amount
     255 bytes from the EGD socket. This can be advantageous,
     since the amount of entropy that can be retrieved from EGD
     over time is limited.



NOTES
     On systems without /dev/*random devices providing entropy
     from the kernel, the EGD entropy gathering daemon can be
     used to collect entropy. It provides a socket interface
     through which entropy can be gathered in chunks up to 255
     bytes. Several chunks can be queried during one connection.

     EGD is available from http://www.lothar.com/tech/crypto/
     (perl Makefile.PL; make; make install to install). It is run
     as egd path, where path is an absolute path designating a
     socket. When RAND_egd() is called with that path as an
     argument, it tries to read random bytes that EGD has
     collected. The read is performed in non-blocking mode.

     Alternatively, the EGD-interface compatible daemon PRNGD can
     be used. It is available from http://www.aet.tu-
     cottbus.de/personen/jaenicke/postfix_tls/prngd.html .  PRNGD
     does employ an internal PRNG itself and can therefore never
     run out of entropy.



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




SEE ALSO
     rand(3), RAND_add(3), RAND_cleanup(3)



HISTORY
     RAND_egd() is available since OpenSSL 0.9.5.

     RAND_egd_bytes() is available since OpenSSL 0.9.6.









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Created 1996-2024 by Maxim Chirkov

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