[chbot] CovidCard implementation - how much storage?

[Bevin Brett]

Storage - 8M devices so 23 bits per device, +/- 5min in the last month so 13 bits for times (if you really care about times), so 4B per contact.  25K contacts stored in 128KB of memory.   1 per minute * 60 min/hour * 8h/day * 30 day = 14K contacts a month working at an overworked supermarket checkout...

Ethernet's 'listen, broadcast if quiet' approach will easily allow all the people in a small area to exchange ID's within 1.5 secs if the transmission time is only 1/250th of the listen time.
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