Defense in depth.
The Mac worker app limits the permissions it requests, long audio is split into shorter shards before dispatch, and the coordinator enforces trust tiers before accepting shard results.
Mac app permissions
The Acorn worker app (Acorn.app) is a macOS menu-bar application built with SwiftUI. The current build is not enrolled in macOS App Sandbox. Its normal operation uses:
- Outbound network — reach the coordinator API and download audio fragments.
- File access (user-selected) — only when the user explicitly chooses a local audio file.
- Keychain access — stores the worker credential securely.
- GPU / Metal compute — used by the Whisper and Parakeet backends to transcribe claimed fragments locally.
The app does NOT request camera, microphone, contacts, location, screen recording, or full disk access. Because App Sandbox is not enabled today, these are application-level limits rather than an operating-system sandbox boundary.
Threat model
Acorn distributed design limits the damage any single worker or coordinator compromise can cause:
- Audio sharding — Per-model shard lengths with overlap (5 min default). Each claim receives shard-scoped audio plus task metadata.
- Trust tiers — new workers are untrusted by default, validated against canary audio.
- Coordinator auth — WebAuthn passkeys. No password to phish.
- API key hashing — keys stored as SHA-256 hashes. Coordinator cannot leak plaintext.
- HMAC-signed webhooks — outbound deliveries signed so receivers can verify the payload.
Data in transit
All coordinator traffic uses HTTPS. No plaintext connections accepted in production.
Reporting a vulnerability.
Email security@acorncompute.com with reproduction steps and your contact details. We respond within two business days. Give us reasonable time to fix confirmed issues before publishing. Valid reports get a public credit (unless you prefer anonymity).