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TAG PRIVACY PROTECTION METHOD, TAG DEVICE, BACKEND APPARATUS, UPDATER, UPDATE SOLICITOR, PROGRAMS THEREFOR AND RECORD MEDIUM CARRYING SUCH PROGRAMS IN STORAGE
TAG PRIVACY PROTECTION METHOD, TAG DEVICE, BACKEND APPARATUS, UPDATER, UPDATE SOLICITOR, PROGRAMS THEREFOR AND RECORD MEDIUM CARRYING SUCH PROGRAMS IN STORAGE
According to a first invention, in response to an access from a reader, a tag device causes its second calculator to read a confidential value from a confidential value memory and to apply a second function F2 which disturbs a relationship between elements of a definition domain and a mapping thereof to generate tag output information. The tag output information is fed to an output section, which then delivers it to a backend apparatus. Subsequently, a first calculator reads out at least part of elements of the confidential value from the confidential value memory, and applies a first function F1, an inverse image of which is difficult to obtain, and a result of such calculation is used to update a confidential value in the confidential value memory by overwriting. According to a second invention, an updater which is provided externally of a tag device updates privileged ID information stored in a tag device into new privileged ID information, the association of which with the privileged ID information is difficult to follow, at a given opportunity.
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