Kryfo hides what you say from the network, the relays and us. On the Onion route it also hides where you connect from and who you are. It cannot protect a phone someone else controls, and it has not been audited yet.
What it protects against
- The network. On the Onion route, Kryfo goes through Tor, using a bridge if Tor is blocked where you are. The Relay and Fast routes are faster and skip Tor, and then the relays see the address you connect from. On every route, your internet provider sees encrypted traffic, not who you talk to or what you say.
- The relays. Messages are carried by relays, sealed twice and sent from a throwaway key, to a mailbox address that belongs to that one conversation and to nobody's identity. No relay can read them. On the Onion route, the relays never learn your IP address or who you are. On the Relay and Fast routes, which skip Tor to be faster, the relays see your IP address, never what you say.
- Seizing our servers. There is no central store of messages, contact lists or accounts to take.
- Your phone number. Kryfo never asks for one, so there is none to link you to, and no address book is uploaded.
- Someone making you unlock the app. A decoy PIN opens an empty Kryfo, as if just installed. Hidden chats open only with their own PIN and leave no trace in the everyday app while they are shut. A wipe PIN removes Kryfo from the phone.
- Someone posing as the developer. The key behind the chat with Marios is built into the app, and every message in that chat is checked against it.
What it does not protect against
- A phone someone else controls. Malware, or someone holding your unlocked phone, sees what you see. No messenger can fix that.
- The people you talk to. They can screenshot, copy or forward what you send, or tell others that you talk.
- Someone watching most of the internet. Tor makes linking traffic expensive, not impossible, and Kryfo sends no cover traffic.
- The fact that you talked. Kryfo keeps metadata to a minimum but cannot erase it. If you send while a contact is online, that timing existed.
- Mistakes in Kryfo itself. The encryption is standard, well-studied code, but the way Kryfo puts it together is new and has not had an outside audit yet. One is planned.
A quick look, not a lab
The decoy PIN and hidden chats are for the moment someone makes you unlock your phone and scrolls through it. They are not built to survive a forensic copy of the phone: a copy can show that Kryfo holds more than it shows, and a short PIN can be guessed against it. Android's own storage and battery figures for the app are not hidden either.
If a forensic copy is what you fear, the wipe PIN is the tool, and not having the data on the phone at all is better still.
Someone who already knows your three words or your handle will see different ones in the decoy, and nothing that arrives for you shows while it is open. A backup made inside the hidden chats carries them, and its size can give that away.
The law
In some countries, refusing to unlock a phone or hiding data from officials is an offence in itself. The decoy never shows invented conversations, because showing made-up messages to officials can make things worse. Know the law where you live and where you travel.
Writing to the developer anonymously
It hides your three words, not your writing style or what you say. On the Relay and Fast routes our relay sees the address you connect from.
Found a problem?
Please tell us privately first. The security page (in English) says how, and what happens next.