A secure and private fingerprint-based authentication system

In this paper we propose a secure and private finge rprint-based authentication system. First the user of the system ought to register his or her fingerprints to a serv er database of fingerprint-minutiae templates, whic h are generated from the original fingerprint images and then are i ns rted with a number of foreign minutiae. Upon aut hentication the same live fingerprint will be measured again to regenerate a template, which will then be matched against the stored templates. The regenerated template will be dscarded once the match is done. The new system is s cure and private because of the insertion of large numbers o f foreign minutiae to the database templates and no other template will be stored. Our testing results show the propos ed system is promising. Introduction Biometric authentication system works in two stages: enrollment and authentica tio . At both stages, a raw image is obtained with some instruments by measuring a live biometric. The raw image is then used for feature generation. Features extracted are ofte n transformed into a template, which contains less data than the raw image. The template generate d at authentication will be matched against the enrolled template. If the score is greater than a system defined threshold, the matching is considered successful, otherwise unsuccessful. The ma in objectives of biometric recognition are user convenience and better security. We believe tha t wider applications of biometric technologies are inevitable and necessary. However, biom etric applications have raised a series of issues that prevent its wide acceptance . Among them the security and privacy issues [1-6] of biometric information are regarded as more important than other issues. In literature a few methods [7-9] has been proposed to address these issues by perturbing the original minutiae of fingerprint templates. In this paper we propose an authenti cation system that protects the security and privacy of biometric information. Specificall y, the system is a clientserver system in which the enrolled fingerprint templates will be modified wi th the insertion of large number of foreign minutiae before they are stored in the server databas e. And the modified templates will be used directly, i.e., without removing the inserted foreign minu tiae upon authentication. If the fingerprints are stolen by a hacker, he would have more dif ficulty to differentiate the genuine minutiae from the foreign minutiae. Thus, the biometric templates are secured. No other biometric information needs to be stored because the new template generated at authentication will only be used temporarily to obtain a matching score and then be discarded. The rest of the paper is organized as the following. In section 2 we test matching n ori inal template (without any foreign minutiae) against the same template inser ted with increasingly larger number of foreign minutiae. In section 3 we test matching an original te mplat against a database of fingerprints in which every fingerprint has been inserted with certain numbe r of foreign minutiae. Section 4 summarizes the paper. Matching templates with foreign minutiae In this section we test matching an original template against the same te mplat inserted with increasingly larger number of foreign minutiae. Nine fingerprints were ran domly selected from the first fingerprint database of Fingerprint Verification Competition 2004 [10] for the testing, as given in Table 1. Note that the first row (labeled with “#Min”) is the numbers of mi nutiae in each fingerprint. The 119 minutiae in FP1 will be used as the sources of foreign minutiae to be inserted into other fingerprint minutiae templates. Also note that the cells in t he lef bottom of the table are left empty due to symmetrical matching. Table 1 Fingerprints and their original matching scores #Min 119 117 113 107 93 72 55 25 21 FP# FP1 FP2 FP3 FP4 FP5 FP6 FP7 FP8 FP9 FP1 837 10 17 15 7 14 6 3 0 FP2 1018 15 14 10 12 8 3 3 FP3 1011 16 12 10 7 3 3 FP4 1007 9 8 9 3 3 FP5 509 9 10 3 0 FP6 489 7 3 3 FP7 499 3 3 FP8 100 0 FP9 131 From FP1 we randomly select 10, 20, . , or 110 minutiae and then insert them into the original minutiae templates of other fingerprints to obtain a new template. On each ste p, ma ch the new template against the corresponding original template to obtain a matching scor e. The matching results are plotted in Fig.1. From Fig. 1 we can see that for nearly every fingerprint, as we step-wised ins ert foreign minutiae into a template, the matching scores remain stable at the beginning. For exampl e, for FP4 the matching scores stay nearly the same after 10 to 30 foreign minutiae are in sert d; for FP5 the matching scores remain at 509 after 10 to 60 foreign minutiae are added. We can also see from Fig.1 that the original number of minutiae plays a role on how man y foreign minutiae can be inserted without significantly affecting the matchi ng score. Unlike FP5 which has 95 minutiae, FP9 only has 21 original minutiae. Therefore, the matching score starts going down after 30 foreign minutiae are inserted and reaches the lowest score a fter 60 minutiae are inserted. The generic conclusion is that a fingerprint with more minutiae can t olerate more foreign minutiae. Fig.1 Matching results after inserting foreign minutiae Inserting foreign minutiae into database In this section we test matching an original template against a database of fingerprints in which every fingerprint has been inserted with certain number of foreign minutiae. Since f ingerprint templates in the database will be stored in the server, inserting foreign minu tiae can protect the security and privacy of the original fingerprint templates. The goal of the testing is to see if inserting foreign minutiae would increase the false matching rates (FM R), i.e., some fingerprints which do not match originally may become a match after inserting foreign mi nutiae. For every fingerprint templates in the database we insert a different set of foreign minutiae. We step-wised add more foreign minutiae to every fingerprint templates. At each s t p we match a randomly selected fingerprint against the database. The results are plotted in Fi g. 2, which shows the results of inserting 0, 10, 20 30, 40 and 50 foreign minutiae. From Fig.2 by comparing the DB+0 graph (Top-left) with other graphs we can see that inserting foreign minuti ae has negligible effects on the matching scores. Thus inserting foreign minutia e to the database does not increase the FMR. 0 100 200 300 400 500 600 700 800 90