An improved technique employs knowledge-based authentication (KBA) based on data stored in a mobile apparatus. The mobile apparatus collects data from sources including email data, web browsing data, accessed YouTube video data, and GPS location data recently stored in the mobile apparatus. From such data, the mobile apparatus builds questions and stores the questions on a database on the phone. Upon receiving a request to access a resource stored in the mobile apparatus from a user, the mobile apparatus selects questions at random and ranks them according to a policy accessible to the mobile apparatus. The mobile apparatus presents the highest-ranked questions to the user. The mobile apparatus grants or rejects access to the resource based on an authentication result that the mobile apparatus generates from answers to the questions submitted by the user.