>Here is an untested and not completely thought out idea:
>
>Lets say you use 16F84s and you have a random number generating routine
>that generates numbers between 0 and 49 and you set aside 7 bytes(56 bits)
>of EEPROM to use in the negotiating sequence. Each bit in this 7 bytes
>would represent a number from 0-49 (bit 0, bit 1...bit 49), the upper 6
>bits would be ignored.
>
>Each pic would be programmed like this:
>
>1.) Clear the 7 bytes of EEPROM and initialize random generator.
>
>2.) Pick a random number N (from 0 to 49). Check to see if the
>corresponding bit in the 7 byte file is set. If it is set, pick another N,
>if not procede.
>
How do you generate a random number? - if all PICs are identical, any
of the normal algorithms will generate the same number!
 The only way I can think of to do it would be to time the (long
prescaled) WDT to a few uS (not too hard), and hope the difference
between the RC WDT osc characteristics due to temp/voltage are
sufficiently different.