Private
Shared-key protection
Messages can be encrypted so both sides need the same key to read the exchange.
Private messaging through sound
Send short encrypted messages through an audio signal
FSK Comm lets one device send a short message as sound and another device receive and decode it.
The experience stays compact: write a message, play the signal, listen on the other side, and read the result.
The stack also includes an optional keyed voice scrambler mode for analog voice experiments.
Transmission pipeline
- ChaCha20-Poly1305 encrypted fragments
- CRC and whitening
- FEC and interleaving
- PHY framing to BFSK PCM
- Recorded PCM burst search
- Frame recovery and validation
Overview
FSK Comm is designed for short point-to-point communication where a message needs to travel through analog audio instead of a traditional network path. The project uses BFSK modulation to carry compact encrypted messages through sound, while keeping optional voice scrambling as a clearly separate secondary mode.
Practical
Built around sound
The app is centered on a simple send-and-listen workflow, turning text into audio and audio back into readable text.
Additional mode
Keyed voice scrambling
An optional voice mode can scramble analog speech for practical obfuscation, separate from the primary encrypted text workflow.
How It Works
1. Write and send
The sender enters a short message and starts transmission from the app.
2. Convert to sound
The message is encoded into an audio signal that can be played and received.
3. Listen and decode
The receiving side listens, records the signal, and turns it back into readable text.
4. Protect the exchange
A shared key is used, so the message is not readable without the correct secret.
Good fit for
- Short point-to-point messages where a compact workflow matters.
- Situations where a shared secret should protect the content.
- Mobile flows where one side sends and the other side listens and decodes.
- Projects that want a focused app flow instead of a full messaging platform.
Voice Scrambler
Optional secondary mode
Alongside short-message transport, FSK Comm can also process voice audio with a keyed scrambler for analog radio and speaker-microphone experiments.
Built for practical playback
The scrambler uses voice-band processing, sync markers, and reversible audio transforms so the result stays recordable and recoverable with the same key.
Kept separate from message mode
This feature complements the BFSK text pipeline. It does not replace authenticated message encryption and is presented as an additional capability.
What to expect
- Useful for obfuscating short voice exchanges in analog audio workflows.
- Runs as a distinct keyed audio transform rather than as part of text-message framing.
- Intended for practical voice masking experiments, not as a claim of cryptographic voice encryption.
- Fits the same Android-oriented, record-and-recover style as the rest of the project.
Android app
send and listen workflow
Encrypted
shared-key message protection
Audio signal
message carried through sound
Voice mode
optional keyed scrambling add-on
Android App
