1. A biometric authentication system comprising: a data storage system configured to maintain, for a group of people, biometric data that includes sorted similarity scores, each of the sorted similarity scores being computed to represent similarity between a corresponding biometric image and a reference image; and a biometric verification system that includes at least one processor, the biometric verification system being configured to: access a biometric image of at least a portion of a person; access the reference image; compute a similarity score that represents similarity between the accessed biometric image and the reference image; search the sorted similarity scores included in the biometric data using the computed similarity score; and output a result based on the search of the sorted similarity scores included in the biometric data using the computed similarity score.