End-to-end encryption secures a message in transit, but out of band key verification mathematically guarantees who holds the device at the other end.
End-to-end encryption protects content only after the sender has the intended recipient's key. A safety number or fingerprint helps people check that the key displayed by their devices matches the key expected for the conversation. It is a verification aid, not a guarantee of a person's legal identity or the security of their phone.
Why a second channel matters
If an attacker can replace a key in the messaging path, checking a number only through that same path may repeat the attacker's answer. Compare the displayed number in person, over a previously trusted call, or through another channel whose identity you can independently establish. A familiar display name is not enough.
What to do when the number changes
A changed number may follow a reinstall, a new device or a security event. Pause before treating it as routine, especially for sensitive conversations. Ask the contact to compare the new number through a separate channel. Review the app's device and key-change notice; do not assume old history or backups will behave the same after a reset.
Livara documents safety numbers for its private direct-chat design on the security page. The step-by-step verification guide shows the user workflow. These are Livara's product statements; they do not substitute for independent testing of a released client.
Limits of the check
Matching numbers helps detect an unexpected key substitution in the checked conversation. It cannot prevent a verified recipient from forwarding content, protect an unlocked or compromised device, hide routing metadata, or provide end-to-end encryption to public channels. A key comparison also cannot establish that every other part of the application is correctly implemented.
