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Image Number 3 for United States Patent #8126150.
Spread of a forged storage medium is prevented suppressing an authentic storage medium's damage and trouble of a owner to the minimum. When there is an update request of user key data, the update history of the user key data concerning the shown above-mentioned medium identifier IDm is referred to. When judged that the update of the user key data concerning the shown medium identifier IDm not being performed within a predetermined period, the update of user key data is performed. The request of a update is refused when judged that the update of the user key data concerning the shown medium identifier IDm being performed within a predetermined period.
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