Karakutu

Karakutu encrypts your message with a key you choose yourself, before you send it. The encryption happens inside your phone; there is no Karakutu server carrying your messages. HOW IT WORKS 1. Agree on a passphrase with the other person — face to face or over the phone. 2. Write your message, enter the key, encrypt. 3. Send the encrypted text with an app you already use. 4. The other person brings the text into Karakutu, enters the same key, and reads it. ENCRYPTION • The key is derived from your passphrase with Argon2id (64 MB of memory, 3 passes) — deliberately slow, to make guessing expensive. • The text is encrypted with XChaCha20-Poly1305. • Cascade mode adds AES-256-GCM on top: two different algorithms, optionally with two separate passphrases. • Integrity is verified — a tampered packet will not open. DESIGN DECISIONS • No account, no sign-up, no phone number, no e-mail address. • The key is never written anywhere; it exists only in memory. • Only encrypted packets are stored on the device; plain text never is. • Packets stop opening in Karakutu after 24 hours by default, and you can shorten that. • No advertising, no trackers, no analytics SDK inside the app. • Interface in English and Turkish. HONEST LIMITS Once you send the encrypted text through a chat app, that copy stays there and Karakutu cannot delete it. Security depends on the strength of the passphrase you choose, and you should never send the key through the same channel as the message. The app blocks screenshots of its own screens with a secure text layer; this works today but is not a guarantee provided by the operating system. SUBSCRIPTION Karakutu Pro is offered as a monthly subscription. New subscribers get the first month free; after the trial the period price is charged to your App Store account. The subscription renews automatically unless it is turned off at least 24 hours before the end of the period. You can manage or cancel it on your iPhone under Settings > your name > Subscriptions. Privacy policy: https://burakolgun.com/en/karakutu/gizlilik Terms of use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/