Template renewal in helper data systems

1. A method for authenticating the identity of a physical object (OBJ) by means of metric data using a helper data system, which helper data system during an enrolment step

generates a first helper data (W 1 ) and a first control value (V 1 ) associated with metric data (X) of a reference object, the method further comprising the following verification steps:

generating a first property set (S 1 ) using a noise compensating mapping (NCM) on information derived from first helper data (W 1 ) and a metric data (Y) associated with the physical object (OBJ) to be authenticated,

establishing a sufficient match between the physical object (OBJ) and the reference object using the first property set (S 1 ) and the first control value (V 1 ), the method further characterized in that it comprises a step of

generating an update data (WUPD) using the first helper data (W 1 ), the first property set (S 1 ) and the metric data (Y), said update data (WUPD) being used for updating the first helper data (W 1 ).

2. A method as claimed in claim 1 , where the update data (WUPD) is chosen such that the updated helper data (W 1 ) in conjunction with metric data (Y) results in a sufficient match during authentication.

3. A method as claimed in claim 1 , where the step to generate a first property set (S 1 ) further comprises the generation of a second property set (C 1 ) using a first mapping (N) on information comprising the first helper data (W 1 ) and the metric data (Y), the step to generate a first property set (S 1 ) uses a noise compensating mapping (NCM) on the second property set (C 1 ) to generate the first property set (S 1 ).

4. A method as claimed in claim 3 , where the step to generate an update data (WUPD) comprises the generation of a third property set (C 2 ) by applying a noise robust mapping (NRM) on the first property set (S 1 ).

5. A method as claimed in claim 4 , where the step to generate an update data (WUPD) comprises the application of a second mapping (M) on information comprising third property set (C 2 ) and the metric data (Y).

6. A method as claimed in claim 4 , where

the step to generate an update data (WUPD) comprises the generation of a first difference measure (DM 1 ) quantifying the difference between the second property set (C 1 ) and the third property set (C 2 ), and where

the update data (WUPD) is generated by applying a third mapping (L) on information comprising the first difference measure (DM 1 ).

7. A method as claimed in claim 3 , where

the step to generate an update data (WUPD) comprises the generation of a second difference measure (DM 2 ) quantifying the difference between the first property set (S 1 ) and the second property set (C 1 ), and where

the update data (WUPD) is generated by applying a third mapping (L) on information comprising the second difference measure (DM 2 ).

8. A method as claimed in claim 1 , where the update data (WUPD) is stored for later reference.

9. A method as claimed in claim 8 , where the method further comprises a step for selecting one out of a plurality of generated and stored update data (WSTOR) to replace first helper data (W 1 ).

10. A method as claimed in claim 8 , where the method further comprises a step for generating a replacement helper data using at least one out of the plurality of generated and stored update data (WSTOR) to replace the first helper data (W 1 ).

11. A method as claimed in claim 1 , where the first helper data (W 1 ) is updated using the update data (WUPD) when a sufficient match between the physical object (OBJ) and the reference object is found.

12. A method as claimed in claim 8 , where the first helper data (W 1 ) is updated using at least one out of the plurality of generated and stored update data (WSTOR).

13. A method for identification of a physical object (OBJ) using a first helper data (W 1 ) and a first control value (V 1 ) associated with a reference object, the method according to claim 1 , further comprising a step for establishing the identity of the physical object (OBJ) as being identical to that of the reference object.

14. A client terminal (TRM) for authenticating a physical object (OBJ) using a first helper data (W 1 ) and a first control value (V 1 ) associated with a reference object, the client terminal (TRM) comprising:

a generation means (GM) arranged to generate a first property set (S 1 ) using a noise compensating mapping (NCM) on information derived from the first helper data (W 1 ) and a metric data (Y) associated with the physical object, and

an establishing means (EM) arranged to establish a sufficient match between the physical object and the reference object using the first property set (S 1 ) and the first control value (V 1 ), and

the client terminal (TRM) further characterized in that the first generation means is arranged to generate an update data (WUPD) for updating the first helper data (W 1 ) using the first helper data (W 1 ), the first property set (S 1 ) and the metric data (Y).

15. A client terminal (TRM) as claimed in claim 14 , where the update data (WUPD) is chosen such that the updated helper data (W 1 ) in conjunction with metric data (Y) results in a sufficient match during authentication.

16. A client terminal (TRM) as claimed in claim 14 , where the client terminal (TRM) further comprises a storage means for storing the update data (WUPD) generated during authentication of said physical object (OBJ) for later reference.

17. A client terminal (TRM) as claimed in claim 14 , where the client terminal (TRM) is arranged to output the updated data (WUPD) generated during authentication of the physical object (OBJ) for storage outside the client terminal (TRM).

18. A client terminal (TRM) as claimed in claim 14 , where the client terminal (TRM) retrieves at least one out of the plurality of generated and stored update data (WSTOR) from the physical object (OBJ) being identified for use in the authentication of said physical object (OBJ).

19. A computer program product comprising program code means stored on a computer readable medium for performing the method of claim 1 when said program product is run on a computer.