Re:A Serverless WebRTC Signaling Protocol Using QR Codes
by martinprins on Monday January 19, 2026 @10:47AM
(#46680277)
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).
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).