Patent ID: 6041704
Filing Date: 2000-03-28
Classification: G07B

Abstract:
A method for operating a postage meter machine for generating a security imprint, said postage meter machine having a digital printer which prints franking information together with a signature on a mail piece in a machine-readable region of a franking format, said franking format having a standard printing width for printing on a print medium surface of a mail piece being transported past said printhead, and control means for generating print control signals for causing said digital printer to print said franking information, said method comprising the steps of:generating an asymmetrical key pair comprising a private write key and a public read key;storing said private write key and an asymmetrical encryption algorithm in said postage meter machine in a postal security device;storing said public read key and a certificate associated therewith in a memory location in a data base at a mail carrier site, said memory location being allocated to a postage meter machine identifier;formatting machine-readable information, to be printed by said digital printer in said machine-readable region of said franking format, containing a digital signature and unencrypted necessary franking information, said unencrypted necessary franking information including at least said postage meter machine identifier, a franking value, and a monotonously continuously variable quantity incorporated in said machine-readable information; wherein said digital signature is generated by encrypting said unencrypted necessary franking information with said private write key before generating said print control signals to obtain an asymmetrically encrypted message having a security level associated therewith said digital signature having fewer bits than an RSA digital signature of a comparable security level, and printing said asymmetrically encrypted message with said digital printer.