Modern messaging apps use end-to-end encryption (E2EE) to guarantee users' privacy. But what if the device itself is compromised, or the user doesn't have access to a device/app with such capabilities? To preserve privacy in such scenarios, we need an external device that:

- Implements a known secure E2EE protocol.
- Is easy and inexpensive to manufacture.
- Has no Internet connection.
- Can comfortably interface with typical communication channels.

This project will attempt to create exactly this kind of device. Using the "ELEGOO Mega 2560 the Most Complete Starter Kit" commercial microcontroller kit, the idea is to build a device that a user can type on and read from, which communicates with an untrusted party (dumb phone, messaging app, etc.) by playing or listening to encoded audio, and implements Signal's Double Ratchet protocol.

Initial estimations support the idea that the Arduino Mega 2560 is (barely) powerful enough to implement such protocol.