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.
8/Feb/2001 0.9.6j RAND_egd(3)
