Type a short message. It's encrypted with AES-256-GCM, packed into ultrasonic tone-chords, and played through your speakers — loud, clear, and repeated with a chirp preamble on each end for reliable detection.
0/180 characters — longer messages take longer to play
This is exactly what will be encrypted and transmitted:
| Frequency band | 18.5–19.9 kHz |
| Tone bins | 8 |
| Tones per symbol | 3 (chord) |
| Symbol rate | ~8/sec |
| Encryption | AES-256-GCM |
| Est. playback time | — |
⚠️ This will play a real ultrasonic tone through your speakers. Most people can't hear it, but some younger listeners, and most pets, may notice it.