Deppis

A metadata-private messenger — a Signal-style chat system designed to hide not just message content but communication metadata (who talks to whom, and when). It combines end-to-end encryption (double ratchet) with cover traffic and an oblivious store-and-notify backend, so a network observer — or the relay operator — cannot tell an active conversation from an idle client.

⚠️ Privacy status of this repository's builds

Until the Phase C PingPong enclave store and its attestation flow are in place, every build is DEV, NO METADATA PRIVACY and is labeled so in code, logs, and UI (Constitution IV). The dev store/notify provide no access-pattern privacy. Do not deploy a dev build as private.

The headless prototype shows the whole path working end to end: two independent engines pair out of band, then a message is delivered metadata-privately through the real Rust obsd sidecar.

scripts/run-demo.sh

The script builds obsd and runs the demo. Expected output:

spawning obsd (real Rust sidecar) on 127.0.0.1:<port> …
backend=Dev  metadataPrivate=false  label="DEV, NO METADATA PRIVACY"
[alice] paired with bob — safetyNumber 92349 49678 63182 72023 82353 36590
[bob  ] paired with alice — safetyNumber 92349 49678 63182 72023 82353 36590
✓ safety numbers match → out-of-band verification succeeds
[alice] round 1: wrote REAL  frame (256B, indistinguishable)
[bob  ] round 1: notified — mail waiting (sender identity NOT revealed)
[bob  ] round 1: retrieved from bffcbbd5…: "see you at dusk"
✓ delivered end-to-end through the real obsd sidecar

Every round each client writes exactly one 256-byte frame (real or cover) and reads once, so active and idle rounds are indistinguishable (FR-012).

Requirements: cargo (Rust) and sbt with JDK 22+ (the crypto layer uses the finalized Foreign Function & Memory API — JEP 454, GA in JDK 22 — to call libsodium). The demo prints the DEV, NO METADATA PRIVACY label.

sbt protocolCore/test crypto/test transport/test server/test   # JVM: property tests + KATs + E2E
sbt protocolCoreJS/test                                        # Scala.js engine under Node
cargo test --manifest-path oblivious-sidecar/Cargo.toml        # Rust oblivious sidecar + invariants

The cross-process integration tests (transport/test) build and drive the real obsd sidecar; they self-cancel if the obsd binary is absent.

JSON in (stdin) → JSON out (stdout). Run them through sbt:

echo '{"sharedSecret":"b3V0LW9mLWJhbmQ="}' | sbt -batch "protocolCore/runMain cli.Pcore handshake-init"
echo '{"senderId":"A","receiverId":"B","counter":1}' | sbt -batch "protocolCore/runMain cli.Pcore retrieval-token"
echo '{}' | sbt -batch "crypto/runMain crypto.Mcrypto kat"     # {"pass":true,"vectors":2,...}
sbt -batch "protocolCore/runMain cli.Pstatus show"             # shows the dev privacy label

See ARCHITECTURE.md for the components, the messaging scenarios (pairing, send, notify-before-retrieval, cover traffic), the encryption layers, and the attestation flow — with diagrams.

The full specification, plan, and task breakdown live under specs/001-metadata-private-messenger/ — start with quickstart.md and plan.md. Non-negotiable constraints are in .specify/memory/constitution.md: no hand-rolled crypto, the DEV, NO METADATA PRIVACY labeling rule, and attestation-not-identity on PING/PONG.