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);
int RAND_query_egd_bytes(const char *path, unsigned char *buf, 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 flexi-
ble than RAND_egd(). When only one secret key must be gen-
erated, 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.
RAND_query_egd_bytes() performs the actual query of the EGD
daemon on socket path. If buf is given, bytes bytes are
queried and written into buf. If buf is NULL, bytes bytes
are queried and used to seed the OpenSSL built-in PRNG using
RAND_add(3).
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 col-
lected. The read is performed in non-blocking mode.
Alternatively, the EGD-interface compatible daemon PRNGD can
be used. It is available from http://prngd.sourceforge.net/
. PRNGD does employ an internal PRNG itself and can there-
fore never run out of entropy.
MirOS BSD #10-current 2007-03-08 1
RAND_EGD(3) OpenSSL RAND_EGD(3)
OpenSSL automatically queries EGD when entropy is requested
via RAND_bytes() or the status is checked via RAND_status()
for the first time, if the socket is located at
/var/run/egd-pool, /dev/egd-pool or /etc/egd-pool.
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.
RAND_query_egd_bytes() returns the number of bytes read from
the daemon on success, and -1 if the connection failed. The
PRNG state is not considered.
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.
RAND_query_egd_bytes() is available since OpenSSL 0.9.7.
The automatic query of /var/run/egd-pool et al was added in
OpenSSL 0.9.7.
MirOS BSD #10-current 2007-03-08 2
