Abstract
This paper presents the design and evaluation of the Visual Identification Protocol (VIP) an innovative solution to user authentication based on pictures and visual memory. Three authentication systems were prototyped and compared with the PIN approach in a longitudinal evaluation (N=61). The study revealed important knowledge about attitudes towards and behaviour with different authentication approaches. VIP was found to be easier to remember and preferred by users, but its usability can be easily disrupted by an inappropriate solution. A detailed error analysis is presented to help understand the limits and constraints of visual memory. This knowledge is instrumental in designing innovative authentication system.