This feature gives Lion users at least some peace of mind when they share content via iChat, Screen Sharing and file sharing.
The authentication certificate has been used by Mac users in the past when talking over iChat, but Lion is taking the feature to the next level over a few more content sharing applications.
Users who sign up for an Apple ID will automatically create a client certification used to authenticate their identity when they share information over content-sharing sites.
Normally capabilities such as Screen Sharing and File Sharing require the user to have an account on the system. However, with Lion’s enhanced authentication functionality, users can enter their Apple ID as an authorized account in order to acquire access.