Biometric score normalizer

• US 6,591,224 B1
• Filed: 06/01/2000
• Issued: 07/08/2003
• Est. Priority Date: 06/01/2000
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Sullivan, Brian M., Hsu, Shi-Ping
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): TSAI, CAROL S W
• Application Number:
  US09/585,211
• Time in Patent Office: 1,132 Days
• Field of Search: 702/179-181, 702/19, 702/321, 702/1.08, 702/124, 702/183, 702/188, 702/189, 382/115-127, 356/71, 340/5.53, 340/5.83, 340/5.52, 340/5.58, 707/6, 713/186, 713/200, 902/3, 902/6, 703/2
• US Class Current: 702/179
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06F 18/256 of results relating to different input data, e.g. multimodal recognition
• CPC Class Codes: G06V 10/811 the classifiers operating on different input data, e.g. multi-modal recognition
• CPC Class Codes: G06V 40/58 Solutions for unknown imposter distribution
• CPC Class Codes: G07C 9/37 using biometric data, e.g. fingerprints, iris scans or voice recognition

Abstract

Method and apparatus for providing a standardized measure of accuracy of each biometric device in a biometric identity authentication system having multiple users. A statistical database includes continually updated values of false acceptance rate and false rejection rate for each combination of user, biometric device and biometric device comparison score. False acceptance rate data are accumulated each time a user successfully accesses the system, by comparing the user'"'"'s currently obtained biometric data with stored templates of all other users of the same device. Each user is treated as an “impostor” with respect to the other users, and the probability of an impostor'"'"'s obtaining each possible comparison score is computed with accumulated data each time a successful access is made to the system. The statistical database also contains a false rejection rate, accumulated during a test phase, for each combination of user, biometric device and biometric device comparison score.

Claims

1. A method for normalizing biometric test scores generated by multiple biometric devices for multiple users, the method comprising the steps of:

for each user enrolled to use each biometric device, maintaining a statistical database containing a standardized measure of accuracy for each possible score of the biometric device for this particular user, wherein the maintaining step includes updating the statistical database each time a user successfully accesses a protected system using at least one of the biometric devices;

obtaining a current score from a biometric device for this particular user; and

converting the current score to a standardized measure of accuracy obtained from the statistical database.

4. A method as defined in claim 1, wherein the step of maintaining a statistical database includes the following steps performed each time a user successfully accesses a protected system during a data gathering phase of operation and provides data to a biometric device:

obtaining current biometric data from this user;

comparing the current biometric data of this user with a stored biometric template of this user obtained during enrollment to use the same biometric device, and obtaining a comparison score from the biometric device;

after each comparing step, updating a count of test comparisons performed for this user, and updating a count of the number of times the comparison score is obtained for this user;

updating the probability of occurrence of each comparison score; and

computing an equivalent false rejection rate from the probabilities of occurrence of the comparison scores, wherein the false rejection rate is computed as the sum of the probabilities of obtaining comparison scores lower than the one obtained in the step of obtaining the comparison score under consideration for this user, and provides an objective measure of convenience of use for this particular user and biometric device.

5. A method as defined in claim 4, wherein the step of converting the current biometric score to a standardized measure of accuracy includes retrieving from the statistical database a false rejection rate corresponding to this user, the current biometric device and the current biometric score.

2. A method for normalizing biometric test scores generated by multiple biometric devices for multiple users, the method comprising the steps of:

for each user enrolled to use each biometric device, maintaining a statistical database containing a standardized measure of accuracy for each possible score of the biometric device for this particular user;

obtaining a current score from a biometric device for this particular user; and

converting the current score to a standardized measure of accuracy obtained from the statistical database;

wherein the step of maintaining a statistical database includes the following steps performed each time a user successfully accesses a protected system using a biometric device;

obtaining current biometric data from this user;

comparing the current biometric data of this user with stored biometric templates of other users enrolled to use the same biometric device, wherein the biometric data of this user are compared as “

impostor data”

with the other user templates, and a comparison score is obtained from the biometric device;

after each comparing step, updating a count of impostor comparisons performed for each of the other users, and updating a count of the number of times the comparison score is obtained for impostor comparisons relative to each other user;

updating the probability of occurrence of each comparison score; and

computing an equivalent false acceptance rate from the probabilities of occurrence of the comparison scores, wherein the false acceptance rate provides an objective measure of security risk for this particular user and biometric device.

3. A method as defined in claim 2, wherein the step of converting the current biometric score to a standardized measure of accuracy includes retrieving from the statistical database a false acceptance rate corresponding to this user, the current biometric device and the current biometric score.

6. A method as defined in claim 2, wherein the step of maintaining a statistical database further includes the following steps performed each time a user successfully accesses a protected system during a data gathering phase of operation and provides data to a biometric device:

obtaining current biometric data from this user;

comparing the current biometric data of this user with a stored biometric template of this user obtained during enrollment to use the same biometric device, and obtaining a comparison score from the biometric device;

after each comparing step, updating a count of test comparisons performed for this user, and updating a count of the number of times the comparison score is obtained for this user;

updating the probability of occurrence of each comparison score; and

computing an equivalent false rejection rate from the probabilities of occurrence of the comparison scores, wherein the false rejection rate is computed as the sum of the probabilities of obtaining comparison scores lower than the one obtained in the step of obtaining the comparison score under consideration for this user, and provides an objective measure of convenience of use for this particular user and biometric device.

7. A method as defined in claim 6, wherein the step of converting the current biometric score to a standardized measure of accuracy includes:

retrieving from the statistical database a false acceptance rate corresponding to this user, the current biometric device and the current biometric score; and

retrieving from the statistical database a false rejection rate corresponding to this user, the current biometric device and the current biometric score.

8. A biometric score normalizer for use in an authentication system having multiple biometric devices and multiple users, the biometric score normalizer comprising:

a statistical database containing, for each user enrolled to use each biometric device, at least one standardized measure of accuracy for each possible score of the biometric device;

means for accumulating data in the statistical database, wherein the at least one standardized measure of accuracy is updated each time a user successfully accesses the authentication system; and

means for converting a raw biometric device score into at least one standardized measure of accuracy by accessing the statistical database.

10. A biometric score normalizer as defined in claim 8, wherein the statistical database contains an equivalent value of false rejection rate for each combination of user, biometric device and biometric devices score, and the means for accumulating data in the statistical database includes:

means for obtaining current biometric data from a user during a test phase of operation;

means for comparing the current biometric data of this user with a stored biometric template of this user obtained during enrollment to use the same biometric device, and obtaining a comparison score from the biometric device;

means for updating a count of test comparisons performed for this user, and updating a count of the number of times the comparison score is obtained for this user;

means for updating the probability of occurrence of each comparison score; and

means for computing an equivalent false rejection rate from the probabilities of occurrence of the comparison scores, wherein the false rejection rate is the sum of the probabilities of obtaining comparison scores lower than the one obtained by the means for obtaining the current biometric data of this user, and wherein the false rejection rate provides an objective measure of convenience of use for this particular user and biometric device.

9. A biometric score normalizer for use in an authentication system having multiple biometric devices and multiple users, the biometric score normalizer comprising:

a statistical database containing, for each user enrolled to use each biometric device, at least one standardized measure of accuracy for each possible score of the biometric device;

means for accumulating data in the statistical database, wherein the at least one standardized measure of accuracy is updated as users attempt access to the authentication system; and

means for converting a raw biometric device score into at least one standardized measure of accuracy by accessing the statistical database;

wherein the statistical database contains an equivalent value of false acceptance rate for each combination of user, biometric device and biometric device score, and the means for accumulating data in the statistical database includes;

means for obtaining current biometric data from this user;

means for comparing the current biometric data of this user with stored biometric templates of other users enrolled to use the same biometric device, wherein the biometric data of this user is compared as “

impostor data”

with the other user templates, and a comparison score Is obtained from the biometric device;

means operative after the means for comparing, for updating a count of impostor comparisons performed for each of the other users, and updating a count of the number of times the comparison score is obtained for impostor comparisons relative to each other user;

means for updating the probability of occurrence of each comparison score; and

means for computing an equivalent false acceptance rate from the probabilities of occurrence of the comparison scores, wherein the false acceptance rate provides an objective measure of security risk for this particular user and biometric device.