1. An apparatus comprising: a memory; a processor configured to cause receiving of a user determination of a pool of images and; the processor being further configured to form from the pool of images a set of images for user authentication; the processor being further configured to divide the set of images into two mutually exclusive subsets: a key image subset comprising images referred to as key images and a decoy image subset comprising images referred to as decoy images; the processor being further configured to produce an assortment of decoy images and key images; the processor being further configured to cause displaying the assortment of decoy and key images; the processor being further configured to cause receiving user identification of images held as key images; and the processor being further configured to verify whether the identification of key images matched with the key images selected by the processor.