Re:Face ID, Touch ID, No ID, PINs and Pragmatic Security
by dredmorbius on Thursday September 14, 2017 @10:53PM
(#15254209)
Both good points. I've been thinking of some contact / button interaction as well, though that's a toss between keeping the device as physically and electrically simple as possible, vs. some level of interaction. A circuit-completion button on a ring might work, which wouldn't require, say, an additional battery. Though battery life would quite likely be years.
Do you have any refs on capacitive coupling? Is that essentially touchscreen devices? How does that fare in exposed / outdoor environments? I'm thinking of wide applications, and something which wouldn't operate at, say, Tokyo Subway levels of use and demand aren't particularly amenable.
(That's tabling the discussion of whether or not you'd want to have per-use charges for transit use or want to offer that as a public service, or only filter based on individuals, etc.)
Field range might be set by speed-of-light delays. Roughly a nanosecond per 30cm (about 10 foot).
Given a 4 GHz clockspeed, your time resolution is about 0.25 nanosecond, or 7.5 cm -- call it 3 inches.
Do you have any refs on capacitive coupling? Is that essentially touchscreen devices? How does that fare in exposed / outdoor environments? I'm thinking of wide applications, and something which wouldn't operate at, say, Tokyo Subway levels of use and demand aren't particularly amenable.
(That's tabling the discussion of whether or not you'd want to have per-use charges for transit use or want to offer that as a public service, or only filter based on individuals, etc.)
Field range might be set by speed-of-light delays. Roughly a nanosecond per 30cm (about 10 foot).
Given a 4 GHz clockspeed, your time resolution is about 0.25 nanosecond, or 7.5 cm -- call it 3 inches.