[Mono-list] For those interested in the Guid class.
Wed, 19 Sep 2001 22:06:26 -0400 (EDT)
On 19 Sep 2001, Miguel de Icaza wrote:
> So it seems like the decent thing to do these days is to use random
> data instead of using a computer Mac address (which raises some
> privacy issues).
e2fsprogs (http://e2fsprogs.sourceforge.net/) comes with libuuid.so. It
exports some functions for generating uuids. If you have e2fsprogs-devel
installed, you should be able to find some info in
/usr/include/uuid/uuid.h. Even if you can't use the library directly,
perhaps the algorithm will be of help.
On my system, the manpages weren't installed by default, but here is what
I found in the source distro's uuid_generate.3 file:
The uuid_generate function creates a new universally
unique identifier (UUID). The uuid will be generated
based on high-quality randomness from /dev/urandom, if
available. If it is not available, then uuid_generate
will use an alternative algorithm which uses the current
time, the local ethernet MAC address (if available), and
random data generated using a pseudo-random generator.
The uuid_generate_random function forces the use of the
all-random UUID format, even if a high-quality random num-
ber generator (i.e., /dev/urandom) is not available, in
which case a pseudo-random generator will be subsituted.
Note that the use of a pseudo-random generator may compro
mise the uniqueness of UUID's generated in this fashion.
The uuid_generate_time function forces the use of the
alternative algorithm which uses the current time and the
local ethernet MAC address (if available). This algorithm
used to be the default one used to generate UUID, but
because of the use of the ethernet MAC address, it can
leak information about when and where the UUID was gener-
ated. This can cause privacy problems in some applica-
tions, so the uuid_generate function only uses this algo-
rithm if a high-quality source of randomness is not avail-
The UUID is 16 bytes (128 bits) long, which gives approxi-
mately 3.4x10^38 unique values (there are approximately
10^80 elemntary particles in the universe according to
Carl Sagan's Cosmos). The new UUID can reasonably be con-
sidered unique among all UUIDs created on the local sys-
tem, and among UUIDs created on other systems in the past
and in the future.
The newly created UUID is returned in the memory location
pointed to by out.
OSF DCE 1.1
Hope this helps,