There is a lot of detail in Authentec's 'Spot-based finger biometric processing method' patent application here if you're interested: http://www.patentgenius.co

There is a lot of detail in Authentec's 'Spot-based finger biometric processing method' patent application here if you're interested: http://www.patentgenius.com/patent/7787667.html http://www.patentgenius.com/patent/7787667.html In short, they store a number of unique sub-regions of each 'enrollment' (a reading resulting in pixel data). These sub-regions – called 'spots' – can then be hashed and matched against future enrollments to provide a correlation score.