HN Showcase
Back to browse
A file transfer protocol for after the internet dies

A file transfer protocol for after the internet dies

by ducklin404·Jul 9, 2026·3 points·0 comments
Visit ProjectView on HN

AI Analysis

●●●BangerWizardryZero to OneBold Bet

QR code file transfer with ECDH encryption when the internet isn't an option.

Strengths
  • •Sliding-window ACK/retry handles reliability over an inherently lossy visual channel
  • •ECDH key exchange with fingerprint verification on a public QR display
  • •20 KB/s throughput is actually usable for small files in emergency scenarios
Weaknesses
  • •Niche use case limits practical adoption for most developers
  • •Webcam requirement means phones without front cameras can't participate
Target Audience

Security researchers and offline-first developers

Similar To

Minidisc · Snapdrop · QR File Transfer apps

Post Description

Built this for the day the internet and every normal way of moving a file stop being an option. Two webcams, QR codes flashing between them, nothing else. The protocol handles reliability with a sliding-window ACK/retry scheme, and does ECDH key exchange with fingerprint verification since a QR code on screen is about as public as a channel gets. Throughput lands around 20 KB/s, slow, but well, it's the only option when you need it. Live demo: https://stare.asilentpond.com Devlog on how it was built: https://youtu.be/q3fQZ-ZXqow

Similar Projects