// Research series
Offline Visual Exchange
Protocol, optical and replay-control decisions for encrypted exchanges between fully offline mobile devices and disconnected verifiers.
3-part series · Read in order
// Reading path
From first question to final consequence.
- Part 1A one-way QR can establish a key, but not a conversation.An ephemeral X25519 key can protect an offline QR for a pre-provisioned verifier, but freshness, replay resistance and sender authentication still require explicit protocol state.
- Part 2Three hundred milliseconds is an operating envelope.Encrypted QR decoding is governed less by cipher choice than by symbol density, module sampling, optics, motion, exposure and the scanner pipeline. A byte budget and a declared test envelope make a…
- Part 3A secure key cannot make a photographed QR fresh.Hardware-backed signing can prove which mobile key produced an offline QR. It cannot, by itself, prove that the image was created for this verifier, this place or this moment.
Three hundred milliseconds is an operating envelope.
Encrypted QR decoding is governed less by cipher choice than by symbol density, module sampling, optics, motion, exposure and the scanner pipeline. A byte budget and a declared test envelope make a sub-second target measurable. An encrypted QR code can fail before the...