Patent ID: 8689340

Claim:
A method for producing a medium, the method comprising: providing a medium comprising a token, the token implementing at least a portion of a keyed function; providing a secret number k; providing a function D having an associated inverse function D âˆ’1 , such that for inputs x and y, D âˆ’1 (x,D(x,y))=y; receiving at the medium, from externally thereto, a plurality of token inputs, each token input being suitable for input to the token; for each one of the plurality of token inputs: inputting the token input to the token and receiving a token output from the token; transmitting at least the token output to a device external to the medium and performing the following in the device external to the medium: converting the token output to a function output o, the function output o representing a result of performing the keyed function on a function input corresponding to the token input; computing D(o,k); and producing an ordered pair, comprising: a function input corresponding to the token input; and D(o,k), thereby producing a plurality of ordered pairs at the device external to the medium; providing a first encryption method and a first encryption key; and the device external to the medium storing the plurality of ordered pairs on the medium, other than in the token; wherein the storing the plurality of ordered pairs on the medium comprises a subprocess selected from a group consisting of: (a) encrypting each ordered pair at the device external to the medium using the first encryption method and the first encryption key; and the device external to the medium storing each encrypted ordered pair on the medium; and (b) encrypting the plurality of ordered pairs at the device external to the medium using the first encryption method and the first encryption key, thereby producing an encrypted plurality of ordered pairs; and the device external to the medium storing the encrypted plurality of ordered pairs on the medium.