We describe the design and implementation of an automatic identity authentication system which uses fingerprint to establish the identity of an individual. An improved minutia extraction algorithm that is much faster and more accurate than our earlier algorithm [12] has been implemented. An alignment-based elastic matching algorithm has been developed. This algorithm is capable of finding the correspondences between input minutia pattern and the stored template minutia pattern without resorting to exhaustive search and has the ability to adaptively compensate for the nonlinear deformations and inexact pose transformations between an input fingerprint and a template. The system has been tested on the MSU fingerprint database. A perfect authentication rate can be achieved with a 15% false reject rate on this data set. Typically, a complete authentication procedure takes, on an average, about 1.4 seconds on a Sun ULTRA 1 workstation.