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US 6,938,023 B1Granted
Method of limiting key usage in a postage metering system that produces cryptographically secured indicium
AssigneePitney Bowes Inc.
InventorsFrederick W. Ryan, Jr., Robert A. Cordery
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Abstract
A method for requiring that a key used in a cryptographic apparatus be changed includes the steps of: storing a constraint value for a non-time parameter of the cryptographic apparatus, the non-time parameter being related to the operation of the cryptographic apparatus; and requiring the key to be changed when an actual value of the non-time parameter is not within a range defined by the constraint value.
Claims3
A metering system that produces cryptographically secured indicium indicative of value dispensed by the metering system, the metering system comprising:
- a key used to produce the cryptographically secured indicium;
- a memory that stores a constraint value for a non-time parameter of the metering system, the non-time parameter associated with the operation of the metering system;
- and
- means for tracking an actual value of the non-time parameter based on actual operation of the metering system, for comparing the constraint value of the non-time parameter to the actual value of the non-time parameter, and for requiring the key to be changed when the actual value and the constraint value have a predetermined relationship.
1 more element
Dependencies are inferred from the claim text.