For a vulnerability in the authentication or anti-replay design, or in an implementation, contact the maintainers privately before opening a public issue. A public advisory follows once a fix is available.

Earshot authenticates every payload with a pre-shared key, one per keyid (spec/SPEC.md §5.2–5.3). What this does and does not cover:

Covered

• Forgery without the key: a 64-bit SipHash-2-4 tag, ~2⁻⁶⁴ per attempt, and an attempt is 25–40 s of audio with no feedback channel.
• Replay and downgrade: a 32-bit monotonic counter carried in each message and stored per keyid in device NVM; counter <= stored is always rejected.
• Unattended hijack right after power-on: first provisioning and large counter jumps require a physical-presence signal (button, or a 60 s power-on window).

Not covered

• Key extraction. The key sits in the transmitter (a web page) and in device firmware. Reading it from either compromises that keyid everywhere. Use per-keyid scoping to limit blast radius.
• Confidentiality. Payloads are authenticated, not encrypted. Encrypt in the application if the configuration carries secrets.
• Denial of service. Anyone can jam the band or play noise; the channel simply stops working while they do.
• A no-button device has a narrow first-provisioning replay window (SPEC §5.5).

The repository contains a demonstration key only. An unmodified build has no security. Generate your own with tools/keygen.py and install the same key in your firmware.