Safety Numbers

A Safety Number is a way to verify that the encrypted connection between you and a specific contact is authentic. In plain terms, it is a human-checkable fingerprint derived from both parties' keys. If both sides see the same number, the conversation is much less likely to be under a man-in-the-middle attack.

The normal way to verify it is to compare the number with the other person in person or through another trusted channel such as a phone call. If the numbers do not match, you should stop sending sensitive information until you know why.

This is a mature habit in Signal and a genuinely useful one for anyone who handles sensitive conversations. What is not yet clear in XChat is how the feature surfaces in the UI, when users are prompted to verify, and where the number lives in the app. Those details probably will not be fully known until the public release.