Cutout · protocol, visualized

Watch a message travel.

Two phones post identical 4 KB envelopes into a rolling wall of mailboxes — the road below. Every tick (30 s in real life, 6 s here) all box numbers rotate. And phones never ask for their mail: they download the whole tick and filter on the phone.

YOUR VIEW — omniscient, for teaching. Nobody actually gets this view.

SERVER VIEW — identical envelopes, unlinkable boxes, unreadable phones.

AAliceunknown phone

← older ticks · deleted after 24 h

NOW

BBobunknown phone

Cover traffic running — both phones post even in silence.

Alice → Bob Bob → Alice Decoy (cover) Fetched, discarded on the phone Server's copy A packet. That's all the server ever sees.

Demo scale: 1 tick = 6 s, 8 mailboxes per tick, max 4 packets per phone per tick. Real Cutout: 30 s ticks, a vast box space, up to 128 packets — which is why only large photos ever spill into following ticks. Everything else lands within a second or two.