Method for certifying public keys used to sign postal indicia and indicia so signed

摘要

A method for certifying the public key of a digital postage meter using a public key encryption system by a certifying authority. A certifying station and a user station, or a digital postage meter, exchange information and the user station and downloads, or the meter derives, a public key from the exchanged information. The certifying station also publishes related information and its public key. A third party can derive the public key corresponding to the meter's private key by operating on the published information with the certifying station public key.