RAND_egd(3) OpenSSL RAND_egd(3)NAMERAND_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);
DESCRIPTIONRAND_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 VALUERAND_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 ALSOrand(3), RAND_add(3), RAND_cleanup(3)HISTORYRAND_egd() is available since OpenSSL 0.9.5.
RAND_egd_bytes() is available since OpenSSL 0.9.6.
3rd Berkeley Distribution 0.9.6m RAND_egd(3)
