The server can introduce people
A Circle server delivers invitations, profiles, and messages. For people you have not saved yet, the app needs one extra human check before treating a key as trusted.
Profile verification
When Circlus asks you to compare a profile.
Most of the time Circlus verifies keys quietly. Sometimes, when a person is not in your contacts yet, the app asks you to compare a short set of technical details before trusting a new connection.
Why this check exists
Circlus is designed so a server should not be enough to silently impersonate another person. The first trust decision still has to be anchored in something you can compare outside that server.
The key identifies the profile
A profile ID and key fingerprint are compact ways to recognize the cryptographic key behind a person’s Circlus profile.
Contacts remember trust
After you save a person in contacts, Circlus can compare future server data with the saved key automatically.
This is not about passwords
You are not sharing a secret. You are comparing public identifiers to make sure both sides see the same public profile key.
What to compare
Use another channel that the Circle server does not control: in person, by phone, on a video call, or in a chat you already trust.
Ask the person to show their profile details
They can open the share-contact screen or the place where Circlus shows profile verification details.
Compare the profile ID
It should match exactly. Long strings are easier to compare by copying or scanning rather than reading aloud.
Compare the key fingerprint
The fingerprint is a shorter visual check of the same key. Grouped characters are only for readability.
Continue only when both match
If both sides see the same values, the app can remember this profile as the one you expected.
When Circlus may ask
The prompt appears only around first trust decisions or unusual key situations, not during everyday messaging.
Adding a contact
When you scan or paste contact details, the app may ask you to confirm that the displayed profile belongs to the person you intended.
Opening a group invitation
If the person who added you to a group is not saved in contacts yet, Circlus asks you to verify that profile before trusting the group history.
Unknown caller
A call from an unsaved profile cannot be treated like a verified contact call until the key has been checked and saved.
Key mismatch
If a saved contact suddenly appears with a different key, Circlus should stop and ask you to refresh trust through a separate contact-sharing step.
If anything does not match
Do not try to “fix” a mismatch by guessing. Treat it as an unresolved trust problem until you can verify the person through another path.
- Do not continue in the current prompt.
- Ask the person to share a fresh contact link or QR code.
- Use a different channel to confirm that the new data is expected.
- If the server or Circle feels suspicious, stop using it and coordinate with participants outside Circlus.