[ILUG] Generate a GUID

[Chris Higgins]

> On Thu, Sep 06, 2001 at 05:32:00PM +0100, Tim O'Donovan wrote:
> > If your machine has an Ethernet card, why not just 
> > use the MAC Address?  That's globally unique.  I'm 
> > pretty sure you could find some C++ code on the web 
> > to get the MAC address.
> 
> the uuidgen mentioned before would be better.
> 
> a) mac addresses are only unique on that ethernet network.

The MAC address burned into the card *is* unique (well, except for the
batch of korean made ethernet cards that all had the same MAC address).

Most cards though, copy this unique address into some RAM on the card,
and then use it from there - so you can change it.

There are some network protocols that set the MAC address based 
on the upper layer network protocol. DECnet IV is one of those.

So - if you can read the real MAC address, it gives you a unique 
starting point. 
>                                                              i know of at
>    least one company that reused ethernet addresses.  i've reused ethernet
>    addresses in order to fool my cable modem (*sniffle*).
> b) multiple users might be on a single machine.
> c) there might be 0 or more than one card.
> 
> as an aside, a useful tool for generating guid's would be a cpuid.
> combine a cpuid, the time (to the millisecond), a users uid and a random
> number and you'd be pretty sure it would be the only one.  intel nixes
> this idea because except for their more modern processors, they don't
> have a cpuid.  pretty much every other processor has one.
> 
> cue ignorant privacy advocates...

Oooohhh flamebait :)
> 
> kevin
> 
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-- 
** Chris Higgins                         e: chris.higgins at horizon.ie **
** Technical Business Development        tel: +353-1-6204916            **
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