Gangan
Like the talking drum that carried secret messages across Empires of old,
Gangan lets you scramble and share confidential messages,
decipherable only with a secret key.
Gangan is a privacy utility that works completely offline. Available for iPhone, iPad, and Mac (via Mac Catalyst).
Features at a Glance
|
Scramble Encrypt messages with a shared cipher key before sending over any channel |
Morse Encode and decode text as Morse code, play or share as a .wav audio file |
Key Exchange Establish a secret key securely using Diffie-Hellman-Merkle, no secrets ever transmitted |
Scramble Tab
The Scramble tab lets a pair of users exchange a secret key and use it to scramble and unscramble confidential messages.
Setting Up a Secret Key
Gangan offers three ways to establish a shared key:
🔐 Secure DHM (Recommended)
Uses Diffie-Hellman-Merkle key exchange, the same cryptography that secures the internet. Each user generates a private/public key pair on their device. The private key never leaves your device. You exchange only public keys, from which both sides independently derive the same shared secret. Neither side ever transmits the actual secret.
For added security, public keys can be transmitted as an encoded Morse audio file, keeping even the key exchange itself off the grid.
After the handshake completes, Gangan briefly shows you the first digits of the derived secret key for confirmation, then hides it forever.
🎲 Generate
Generates a random passphrase. Share it with the other person verbally or in person, and both enter it to derive matching keys.
✏️ Enter
Manually enter a passphrase you’ve agreed on with the other person.
Using the Key
Once a key is active:
- Scramble, encrypts your message and copies it to the clipboard, ready to paste into any app
- Unscramble, decrypts a scrambled message from the other user
Session timeout: A configurable auto-expiry timer clears the secret key automatically (15 min, 30 min, or 1 hour), on both iOS and Mac.
Morse Tab
The Morse tab converts text to and from Morse code with two modes:
| Mode | Description |
|---|---|
| Plain | Standard Morse code, no encryption |
| Cipher Key | Morse output is encrypted with your shared secret key |
Both modes support:
- Encoding text to Morse code (dots and dashes)
- Decoding Morse code back to text
- Live Morse signal visualiser and waveform display
- Playing Morse audio directly on the device
- Downloading and sharing as a
.wavaudio file - Importing a
.wavfile for automatic Morse decoding
How the Key Exchange Works
Security Notes
- All processing happens locally on your device, no data is ever sent to a server
- The secret key is stored only on your device and is never transmitted
- Once a key is cleared or expires, scrambled messages cannot be recovered, even with the app, without re-establishing the same key
- You are responsible for how you share the output of this application. Exercise appropriate caution with sensitive information.
Privacy Policy
No user data is collected.
Gangan works completely offline and does not connect to the internet.
It does not store your messages, keys, or any processed output.
Contact the Developer
Click the View on GitHub button above to raise issues, request features, or give feedback. Or reach out via email at alakobanks@icloud.com.