| 摘要 |
A key control system comprises the generation of a first set of predetermined keys K pred which are then used as master keys for a plurality of respective postage meters. The keys are then related to a respective meter in accordance with a map or algorithm. The predetermined master key K pred is encrypted with the date to yield a date dependent key K dd related to the respective meter. The date dependent key is encrypted with a unique identifier or the respective meter to yield a unique key K final that is by the respective meter to generate digital tokens. The Data Center encrypts the date with each predetermined key K pred to yield a table of dependent keys K dd's. The table of K dd's are distributed to verification sites. The verification site reads a meter's identification from a mailpiece being verified to obtai n the dependent key K dd of the meter. The verification site encrypts the dependen t key K dd with the unique identifier to obtain the unique meter key which is used to verify tokens generated by the meter. In the preferred embodiment, the master key K pred, the date dependent key K dd, and the unique key K final, in the meter are stored in the meter. In an alternate embodiment, the master key K pred is encrypted with a unique meter identifier to obtain the unique k ey K final which is stored in the meter. The meter then generates its date dependent key K dd, which is used to generate digital tokens.
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