[Opendispense] Re: [ucc] Vending machine authentication ideas?

[Bernard Blackham]

On Wed, Jun 23, 2004 at 03:23:44AM +0800, Bernard Blackham wrote:
> Can anybody suggest something suitable?

With all the suggestions, I've gone for the following:

Snack machine stores a 16-character key, and an increasing sequence
in NVRAM. If the overriding dip switch isn't set, it presents a
challenge to the client if they wish to vend something.  The client
must compute CRC16(challenge + secret + message) and attach it to
the message, and the snack machine does similarly.

This seems sufficient to be a deterrent, though given enough time
a determined individual could probably crack it.

Thanks for all the suggestions :)

I'm also at the point where I believe the ROM is about as full and
packed with features as needed (and will fit!). It even contains
it's own source code downloadable via xmodem, should it be lost in
10 years time.

There are also commands to peek and poke random bytes of memory so
that extra code can be tried out without burning another EPROM. (eg,
for testing peripherals when they come).

Bernard.

-- 
 Bernard Blackham <bernard at blackham dot com dot au>