Hi All,
A quick progress update on Signing Room and the stateless PSBT coordination BIP draft.
Last week I tagged v3.4.0 of the coordinator and v1.2.0 of the SDK. The primary focus of this release is introducing Role-Based Access Control (RBAC) without introducing accounts, database state, or leaking participant identities to the relay.
Previously, the protocol operated on a binary access model (Coordinator vs. Guest), where any connected peer could download, sign, and broadcast updates to the PSBT. In institutional, legal, or high-security multisig workflows, separation of duties is critical. Transactions often require off-chain witnesses, compliance officers, or observers who need real-time verification of outputs and signatures without having the capability to submit signatures or manipulate the state machine.
To maintain zero-knowledge relay architecture:
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The room initiator generates role-scoped capability tokens derived from the root session entropy inside the browser. Key material resides strictly in the URL fragment (
#) and is never transmitted over HTTP. -
Capability tokens encapsulate signed policy scopes (e.g.,
can_propose,can_sign,witness_only). The relay enforces these permissions ephemerally in RAM: if an unauthenticated socket or an observer without signing privileges attempts to dispatch a signature payload, the relay rejects the frame. -
Joining clients decode their role privileges locally from their fragment token, enabling the interface to adapt deterministically (restricting signing prompts for auditors while providing verification tooling).
Updates & BIP Specification
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Release notes and implementation details: Release v3.4.0 - Zero-Knowledge RBAC · scarlin90/signingroom · GitHub
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Updated the BIP draft with the revised URL fragment schema, capability token message formats, and test vectors:
I am currently working on Tapscript / BIP 371 support to expand beyond native SegWit multisig and accommodate Miniscript spending trees.
Feedback and critiques on the token derivation and message format are welcome.
Best regards,
Sean Carlin