[Interest] Unique - Hardware bound - ID

Konrad Rosenbaum konrad at silmor.de
Thu May 16 09:12:29 CEST 2013

Just in case, two things I forgot: 

Many (if not most) computers have several MAC addresses. The laptop I'm 
writing this on has six network interfaces, four with a hardware address and 
of those three with an actual MAC:

* Ethernet device (built in, fixed MAC, which I did not bother to change)
* WLAN device (also built in, no bother at the moment, but I did change it a 
few months ago to be able to use a misconfigured WLAN)
* virtual Localhost adapter (no HW addr)
* virtual Teredo adapter (something longish made of zeroes that claims to be a 
HW addr)
* virtual ethernet device (with a random MAC that changes every boot)
* depending on loaded kernel drivers: a Firewire network adapter with a 
longish non-MAC HW addr

The same is true of most other hardware, many computers have more than one 
hard disk, more than one CPU core, etc.

Even more devastating: hardware tends to change. I've been known to connect 
two additional real ethernet cards to my laptop and then add a couple more 
vitual adapters - just for experimentation.

Unfortunately you can't tell which ones are built in, which ones are plugged 
in and which ones are purely virtual.


* store all of them and insist that one or two remain
* never assume the computer will look the same after a reboot even if it is 
the same computer
* maybe: offer the user to bind to one specific instance
* plan ahead for users who lose some piece of hardware (HD crashes, burnt out 
ethernet cards, change of PC/laptop, etc.)

Soft piece of advice: don't assume that you can solve this problem 100%. 
Others have tried before and all of them failed one way or another. Keep 
yourself flexible enough to handle unexpected situations outside the software.


On Wednesday 15 May 2013 13:07:05 you wrote:
> I believe the mac address will suffice. In addition I will probably some
> other hardware related data and create a hash from it. I emagined there
> would be a solution for this problem but it semes its not that easy.

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