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Message encryption using the Kryptos keyboard in your conversations. Incoming ciphertext is decrypted on screen. Messages are visible only to you. Works on top of messaging apps and SMS. Different use cases allow for confidential communication over insecure messaging apps.
Kryptos works natively between iPhone and Android without accounts or servers. Encryption keys are stored on the device.
iOS: the .ipa is unsigned, you sign it on the device. Android: allow installs from unknown sources.
Open source github.com/swisslite/Kryptos Support the project.ipa 10ad030b01852130ce829095cd6ff849afb3992d000bd080a9d24196d2edf187
.apk 00c6a3565959498709a4458f30e540df3f9125d63c55ba4706f44e17d854f492
Key features: encryption based on libsignal, encryption over messaging apps and SMS, hiding messages in images, message masking in stegotext, and more.
Enter a message in Kryptos or using the built-in Kryptos keyboard while in a messaging app. Tap the “”, and the text is encrypted in the message field.
Send the encrypted text through Telegram, WhatsApp, SMS, or any other messaging app. To a third-party observer, the ciphertext looks like an ordinary string of characters, with no way to recover the contents of the original message.
Kryptos decrypts the received ciphertext in the messaging app and displays the original message on screen. The message can also be decrypted through the keyboard or in the app from the clipboard.
The same encryption as Signal, using the libsignal library: a new key for each message (Double Ratchet) and protection against future attacks using quantum computers (PQXDH and SPQR). It is also possible to pad message lengths to fixed values to make ciphertext analysis by third-party observers more difficult.
No internet connection. The app contains no network code, and encryption keys, settings, and chat history are stored locally.
A native app for both platforms with full compatibility. Messages, keys, and ciphertext hidden inside images or text work between both sides.
On Android, Kryptos works over other apps: it detects ciphertext and displays the decrypted text over the ciphertext in the chat. There is no need to copy the ciphertext separately. On iPhone, copied ciphertext can be decrypted by the keyboard from the clipboard or by “” above the keys, or in the Kryptos app, also from the clipboard.
The Kryptos keyboard is installed as a system keyboard and is available in any app where text input is used. Enter a message, tap “”, and the ciphertext remains in the input field, ready to send. The keyboard can also decrypt incoming ciphertext above the keys. Suggestions and autocorrection are supported for multiple languages, as well as emoji. The key text size and vibration level can be configured. Other settings are also available. The keyboard works offline.
Hide a message inside an image or disguise it as an ordinary set of words instead of obvious ciphertext.
Use a shared password: agree on a password with another person and exchange information using symmetric encryption. PGP is also supported.
Biometrics, hiding content in the app switcher, screenshot blocking, and automatic clipboard clearing.
A separate PIN code that, instead of unlocking the app, deletes all keys, chats, and contacts.
No. You stay in your own messenger: type the message, tap the lock on the Kryptos keyboard, and only the ciphertext is left in the field. An incoming message is shown decrypted right over the ciphertext on Android, and read by that same keyboard on iPhone. You open the app itself only to add a contact or change a setting.
You enable it once in the system list of keyboards, and it is then available in any app. Pick a contact, type, tap the lock: the plain text in the field turns into ciphertext. Incoming messages are read in the same place: you copy the message and the keyboard shows the decrypted text above the keys with the sender's name. You can also type in a field inside the keyboard itself, and then the messenger never sees the plain text at all. The rest of the time it is an ordinary keyboard, with suggestions and autocorrect for Russian, English, German, Persian and Brazilian Portuguese, pinyin input for Chinese, fully offline.
It is an Android feature. You switch the Kryptos service on once in the accessibility settings, and the app then finds its own ciphertext on screen and lays the decrypted text over it while you scroll the conversation. Nothing to copy, nothing to open. The service reads only text that is already on the screen, works only for your contacts, and never while Kryptos is locked. A separate switch blocks screenshots while it runs. The iPhone gives no app that kind of access to the screen, so there the keyboard does the reading.
Enable the Kryptos keyboard in the system list of keyboards: on iPhone you also allow it full access, without which it cannot reach the keys. On Android, if you want on-screen decryption, switch the service on in the accessibility settings. And exchange keys with your contact: let them scan your QR code, or just copy your key as text and send it any way you like, through that same messenger if you want. Their key is pasted as text in the same way, no camera needed. That key is the public one and it is safe to show; the private key never leaves the device. After that there is nothing to configure and nowhere to register.
Yes, nothing but Kryptos can decrypt the message. Which phone each of you carries does not matter though: the iPhone and Android versions are fully compatible, and keys and messages work in both directions.
No. Kryptos has no servers and no accounts, and there is not a single line of networking code in the app. On Android it does not even ask for permission to reach the network. Encryption happens entirely on the device, and delivery is handled by whatever messenger you already use.
No, it only ever gets text that is already encrypted. It does still see that you sent something, to whom, and roughly how much. That is metadata, and Kryptos does not hide it, but you can at least mask the length in Settings → Privacy.
Chats use Signal's own libsignal library, the same protocol as Signal itself, with post-quantum protection on every message, not just the handshake. Password mode and photos use Argon2id and AES-256-GCM. Kryptos contains no home-made cryptography.
It carries the post-quantum handshake (PQXDH with Kyber), which is about two kilobytes. It is sent once: as soon as your contact replies, messages become many times shorter.
That is not a fault but forward secrecy: the key for each message is destroyed the moment it is read, so old correspondence cannot be recovered even by someone who takes your phone. Messages you have already opened remain in the chat history.
Usually the wrong contact or the wrong profile is selected. If every new message from one person fails, the session has gone out of sync: send them your key again and have them add you a second time.
It is a fingerprint of the key. Compare it with your contact over some other channel, read it out loud for instance. If the numbers match, there is definitely nobody in the middle.
A profile is a separate identity with its own key and its own contacts. You can keep several and switch between them, to keep work and private life apart for example.
No. A conversation runs from one device: its key chain cannot advance in two places at once. Move your keys to the new phone with a key backup and then use only that phone.
The keys live on the device and nowhere else, so deleting the app destroys them for good and there is nothing left to decrypt with. The only insurance is to make a key backup in Settings beforehand. The flip side of the same property: whoever finds the phone gets nothing either.
Only if “Back up chats” was on when the file was made. Otherwise the file carries only your keys, your contacts and your PGP keys.
There is no way to recover it. The file is encrypted with that password and Kryptos keeps no copy of it anywhere. Make a fresh backup with a password you will not forget.
They erase the conversation inside Kryptos after the time you pick, on your device, and on your contact's if they set the same thing themselves. What they cannot touch is the ciphertext already sitting in the messenger: only the messenger itself can remove that.
No, Kryptos encrypts text only. The Photo tab does something different: it hides a text message inside a picture, rather than sending the picture itself securely.
The photo has to be sent as a file (a document). Sent as an ordinary picture it is recompressed by the messenger, and recompression destroys the hidden data.
It is a second password for the lock screen. Type it instead of your normal passcode and the app silently and irreversibly destroys every key, message and setting, then opens as if it had just been installed. You set it up in Settings → Privacy.
Only to scan a contact key from a QR code. The camera is used nowhere else, and refusing access breaks nothing: you can always paste the key as text instead.
No. On iPhone the keys sit in the Keychain marked as this-device-only, so they never go into an iCloud or computer backup. On Android the app is excluded from cloud backup and from device-to-device transfer entirely. Everything else is encrypted with exactly those keys, so a stray copy would be unreadable anywhere else.
iOS 17 and later. An unsigned .ipa file is used and signed on the device.
Android 8.0 and later. Signed .apk. Installation requires allowing apps from unknown sources.
Not used. The app runs locally and does not use a network connection.
Russian, English, German, Chinese, Persian, and Brazilian Portuguese. The interface language is determined by the system language settings.