Aspects of the invention pertain to preserving the privacy of users in on-line systems while also enabling verification that the users are who they purport to be. Confidential personal information may be communicated from a user to a trusted third party via a web-based application or other service. However, the personal information is encrypted so that the application or service is unable to access it. The trusted third party accesses the personal information and uses it to verify that a user ID such as an email address is associated with a particular user. This information is provided to the web-based application or service to certify the identity of the user. As a result, the application or server verifies to other users that the certified user is who he/she purports to be.