martinprins

Thanks! The write-up took longer than the actual protocol design.

Author here. Started with a simple problem: sync data between two phones with no backend.

WebRTC signaling SDPs are ~2.5KB. Too large for practical QR scanning. When you control both endpoints, most of that is unnecessary ceremony.

Key insights: derive ICE credentials from DTLS fingerprint via HKDF, use binary encoding (IP as 4 bytes not ASCII), skip compression (DEFLATE increases size on high-entropy data), skip base64 (QR supports raw binary).