Revocable biometrics with robust distance metrics
View Patent ↗Techniques, systems and methods relating to cryptographically secure revocable biometric signatures and identification computed with robust distance metrics are described. Various biometric cryptographically secure revocable transformation approaches are described that support a robust pseudo-distance computation in encoded form, thereby supporting confidence in verification, and which can provide for verification without identification.
1. A method for secure revocable identity tokens, comprising the steps of:
a) capturing a biometric signature having a plurality of feature vectors;
b) transforming each of the plurality of feature vectors into a stable portion and a residual part
c) cryptographically encoding the stable portion to form a secured part and simply transforming the residual portion to be the residual part.
2. The method of claim 1 , wherein step (b) further includes the step of:
b1) transforming at least one of the plurality of feature vectors and dividing it into a most significant bits portion and a least significant bits portion;
b2) securing the most significant bits portion.
3. The method of claim 1 , wherein step (c) includes the step of using a public key encryption to produce at least part of the secured part.
4. The method of claim 1 , where it is computationally intractable to recover the original feature vectors from any combination of the secured and the residual part.
5. The method of claim 2 , wherein step (b2) includes the step of including a password as part of the process of generating the secured part.
6. The method of claim 5 , wherein the password is not stored in a computer readable medium after completion of step (b2).
7. The method of claim 1 , further including the steps of:
c) comparing the secured part of the one of the plurality of feature vectors to an associated secured part of a stored feature vector;
d) when a closeness measure of the secured parts is within a predetermined threshold, comparing a residual part of the one of the plurality of feature vectors to an associated residual part of the stored feature vector.
8. The method of claim 7 , further including the step of:
e) repeating the comparing steps for all of the plurality of feature vectors to form a closeness score.
9. The method of claim 8 , wherein the closeness score is essentially equal to a standard closeness score of the biometric signature.
10. A method for secure revocable identity tokens, comprising the steps of:
a) receiving a biometric signature having a plurality of feature vectors;
b) transforming each of the plurality of feature vectors and splitting each into a probe secured part and a probe residual part; and
c) comparing the probe secured part of one of the plurality of feature vector to a gallery secured part of an associated gallery feature vector.
11. The method of claim 10 , further including the step of:
d) when the probe secured part and the gallery secured part are not equal, assigning a threshold closeness measure.
12. The method of claim 11 , further including the steps of:
e) when the probe secured part and the gallery secured part are equal, measuring a closeness of the residual part to a gallery residual part to form a closeness measure;
f) when the closeness measure is greater than the threshold closeness measure, assigning the threshold closeness measure.
13. The method of claim 12 , further including the step of:
g) when the closeness measure is not greater than the threshold closeness measure, using the closeness measure.
14. The method of claim 10 , wherein step (b) further includes the step of:
b1) encrypting the probe secured part using a public key encryption.
15. The method of claim 10 , wherein step (b) further includes the step of:
b1) password protecting the probe secured part.
16. A method for secure revocable identification, comprising the steps of:
a) receiving a probe biometric signature having a plurality of probe feature vectors;
b) transforming each of the plurality of probe vectors into a secured part and a residual part to form a probe identity token; and
c) determining a closeness measure between the probe identity token and a gallery identity token.
17. The method of claim 16 , wherein the step (b) further includes the step of public key encrypting the secured part.
18. The method of claim 17 , wherein step (c) further includes the step of:
c1) receiving a password.
19. The method of claim 17 , wherein step (c) further includes the step of:
c1) comparing the secured part to a gallery secured part;
c2) when the secured part and the gallery secured part are not equal, assigning a threshold closeness measure.
20. The method of claim 19 , further including the step of:
c3) when the secured part and the gallery secured part are equal, measuring a closeness of the residual part to a gallery residual part;
c4) when the closeness measure is greater than the threshold closeness measure, assigning the threshold closeness measure;
c5) when the closeness measure is not greater than the threshold closeness measure, using the closeness measure.
21. A secure revocable identification method, comprising the steps of:
a) creating a first identity token having a secure part form a biometric signature; and
b) creating a second identity token derived from the first identity token without use of the biometric signature, wherein the second identity token is not identical to the first identity token and a transformation from the first identity token increases a potential space associated with the second identity token.