| 摘要 |
A key control system comprises the generation of a first set of predetermined keys Kp red which are then used as master keys for a plurality of respective postage meters (12). The keys are then related to a respective meter (12) 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 (12). 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 (16) 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 obtain the dependent key K dd of the meter (12). The verification side (34) encrypts the dependent key K dd with the unique identifier to obtain the unique meter key which is used to verify tokens generated by the meter (12). 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 the alternate embodiment, the master key K pred is encrypted with a unique meter identifier to obtain and the unique key K final which is stored in the meter (12). The meter then generates its date dependent key K dd , which is used to generate digital tokens.
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