Safety number

Your conversation is encrypted: it cannot be read on our server or on the way. But encryption leaves one question open, and it is not a small one: are you writing to the right person?

Imagine somebody stepping in the middle and handing you their keys instead of your contact’s. The conversation is still encrypted — only now it is encrypted for them. From the outside everything looks perfectly normal.

That is what the safety number is for. It is sixty digits computed from your keys and your contact’s keys. The two of you get the same number. If you compare them and they match, nobody is in the middle.

Where to find it

My Contacts → the person → Safety number.

How to compare

Do not compare it inside the conversation itself: if somebody is tampering with it, they will tamper with the digits too. Use any channel where you can recognise the person for certain:

• Out loud. Read the digits in person or on a call. They are split into twelve groups of five on purpose, so you do not lose your place.
• By code. If you are next to each other, both open this screen and tap “Scan their code”. The app will tell you whether it matched.

If it matched, tap “Mark as verified”. The mark stays in the contact card.

The mark is kept on this device

It is never sent anywhere — not to us, not to your contact. It is your own observation: you compared the digits with your own eyes, on this particular phone. On another device of yours you will have to compare them again.

If the number has changed

The screen shows this as a red banner: today’s number is not the one you verified.

Usually the reason is ordinary:

• your contact changed phones or reinstalled the app;
• they restored their account with a recovery phrase;
• their keys changed after they lost a device.

But an impersonation looks exactly the same. So:

1. Do not send anything sensitive until you know which it is.
2. Compare the number again — by voice or by code, and not inside this conversation.
3. If it matches, mark it verified again. If it does not, and your contact says they changed nothing, the conversation cannot be trusted.

What the safety number does not do

• It does not protect you from someone holding your contact’s unlocked phone: to the device that is the same person.
• It does not tell you who is in front of you in real life. It says one thing only: since the minute you compared the digits, you have been talking to the same device with the same keys.