Independent research/development project · technical preview

Research provenance: paper, SignalCD, authors’ PoC, and this repository

Purpose

This document makes the relationship between the research work and SignalCD Modern PoC explicit. It is intended to prevent two opposite mistakes: hiding the research lineage, or implying that this repository is the paper authors’ official implementation.

Canonical relationship

flowchart LR
  P[Knabenhans, Maradni, Troncoso<br/>End-to-End Encrypted Collaborative Documents<br/>USENIX Security 2026]
  F[Generic E2EE-CD construction<br/>encrypted asynchronous broadcast<br/>+ strongly convergent reconciliation]
  S[SignalCD<br/>paper instantiation using Signal]
  U[spring-epfl/signal-collaborative-documents<br/>authors' research prototype]
  M[SignalCD Modern PoC<br/>independent modern implementation]

  P --> F --> S
  S --> U
  S --> M
  U -. reviewed and pinned as upstream evidence .-> M

What comes from the paper

The paper provides the architectural construction and security/correctness requirements that motivate this repository: client-side strongly convergent reconciliation combined with an end-to-end encrypted asynchronous broadcast channel, plus document-sharing, lifecycle, confidentiality, integrity, and participant-list requirements.

The project tracks these requirements as R1–R10 in docs/POC-REVIEW.md and uses them as design and test targets. The paper is a design/provenance source, not code copied into the modern implementation.

What comes from SignalCD

SignalCD is the paper’s Signal-backed instantiation of the generic construction. It demonstrates that Signal group messaging can carry collaborative-document updates while a client-side reconciliation layer converges document state.

This repository keeps the SignalCD name visible because that is the most accurate description of the concrete research lineage being explored. The public project name adds Modern PoC to distinguish this work from the paper authors’ system and from any official Signal product.

What comes from the authors’ prototype

The authors’ prototype is preserved as a pinned Git submodule:

upstream/
  https://github.com/spring-epfl/signal-collaborative-documents
  pinned commit: 2b96245a484ad651b74afead945478c40084728f

The prototype is used as implementation evidence for:

Automerge incremental updates;
Signal group-message transport;
asynchronous/concurrent-edit benchmark scenarios;
the feasibility of composing reconciliation with Signal delivery.

It is not treated as the application codebase. SignalCD Modern PoC has its own client, protocol, persistence, identity, authorization, sidecar, web UI, tests, and Android work.

What is original to this repository

Area	SignalCD Modern PoC contribution
Browser architecture	Vite/React client with a framework-neutral collaboration client layer
Protocol	Versioned binary envelopes, validation, chunking, deduplication and recovery semantics
Local-first durability	IndexedDB persistence, durable outbound replay, checkpoints, restart behavior
Application identity/E2EE	Browser-owned Ed25519/X25519 identity and recipient-bound encrypted envelopes
Authorization	Signed authorization roots/history, replay resistance, fork detection/resolution
Sidecar boundary	Hardened localhost WebSocket ↔ `signal-cli` JSON-RPC/SSE adapter
Fault evidence	Deterministic delay/reorder/duplicate/drop/offline transport testing
Android	Kotlin protocol/storage/session/sidecar compatibility scaffold and tests
Operator/research UX	Inspector/guided views, status and recovery evidence

Naming and compatibility

The public project name is SignalCD Modern PoC and the GitHub repository is signalcd-modern-poc.

Compatibility-sensitive identifiers from the earlier implementation name remain unchanged in the 0.x line:

package scope @e2e-col/*;
environment variables E2E_COL_*;
Signal message namespace e2e-col:v1:;
IndexedDB/localStorage names;
Android Java/Kotlin namespace dev.e2ecol.*;
existing e2e-col:// deep links.

Changing those is a protocol/storage/API migration and is intentionally separate from the public-facing rename.

Affiliation statement

SignalCD Modern PoC is an independent research/development project. It does not claim authorship of the paper, ownership of the authors’ prototype, or affiliation with Signal Messenger LLC, the Signal Foundation, EPFL, the Max Planck institutes, or the named paper authors.

Use of “SignalCD” identifies the research construction being implemented and evaluated. “Signal” and other third-party marks remain the property of their respective owners.

References

Christian Knabenhans, Zayd Maradni, Carmela Troncoso, End-to-End Encrypted Collaborative Documents, 35th USENIX Security Symposium, 2026. https://www.usenix.org/conference/usenixsecurity26/presentation/knabenhans
SPRING/EPFL, signal-collaborative-documents research prototype. https://github.com/spring-epfl/signal-collaborative-documents
Local implementation review: POC-REVIEW.md
Architecture: ARCHITECTURE.md
Requirements/roadmap: ROADMAP.md