Hi everyone,
I'd like to propose a new BIP for real-time, trust-minimized coordination of multi-signature PSBTs.
The Problem
Coordinating N-of-M Bitcoin transactions currently forces users into a binary choice:
- Manual out-of-band transfers (USB drives, secure messengers) that preserve privacy but introduce high friction and error risk, or
- Stateful coordination servers that offer good UX but act as privacy honeypots, logging metadata, signer relationships, and often storing PSBTs on disk.
The Proposal: Blind Relay
This BIP introduces a "Blind Relay" - an ephemeral, stateless, zero-knowledge WebSocket relay. All payloads are encrypted client-side with AES-GCM-256, with decryption keys held exclusively in client-side URL fragments (never sent to the server). The relay operates entirely in RAM with a strict 24-hour TTL and self-destructs upon completion, providing real-time coordination without persistent metadata or disk storage.
A reference implementation has been running in production for three months, successfully facilitating real multisig ceremonies.
Links
- BIP Draft: https://github.com/scarlin90/bip-stateless-psbt-coordination/blob/main/bip-draft.md
- Source Code: https://github.com/scarlin90/signingroom
- Live Client: https://signingroom.io
- Related Research Paper: https://arxiv.org/abs/2601.17875
I look forward to your technical feedback - especially on the specification, security model, edge cases, and any suggested improvements.
Best regards,
Sean Carlin
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