Someone's safety number changed
TACENZA Chat locks a chat when a contact's key changes, until you compare safety numbers. What it means, how to check, and when to be careful.
When a contact’s key changes, Chat shows “The key for … has changed. That can mean a new account – or someone pretending to be them.” and won’t send until you’ve checked. Usually there’s a harmless reason, such as the person deleting their account and making a new one with the same name. But check before you write.
How to check
- Contact the person another way you trust – in person, or on a call where you recognise their voice. Don’t ask in the TACENZA chat itself.
- Open their profile and choose Safety number. You’ll see 12 groups of 5 digits.
- Compare the numbers with what they see on their phone for you. They should be the same on both devices.
- If they match, choose I’ve verified it in the chat, or Mark as verified on their safety number.
If they match, nobody is sitting in between you, and the chat opens again.
If the numbers don’t match, or the person says they haven’t changed anything, don’t send anything sensitive. Someone may be trying to read along. Block them if you’re unsure – see How do I block someone?
Why it happens
Each account has its own keys, made on the device when the account is created. The first time Chat sees someone’s keys, it remembers them. If the server ever hands out different keys for that person, Chat notices and stops, instead of quietly encrypting to the new keys.
Changing a password or logging in on a new device doesn’t change keys, so a key change is worth asking about.
Keeping track
- Settings › Security Center lists your contacts’ safety numbers, and whether you’ve verified them.
- A verified badge shows only while the keys stay the same. If they change, the badge goes away, so you’ll know.
Read more: Privacy and safety settings in the docs.
Still stuck?
If a chat stays locked after you’ve confirmed the safety number, contact support.