US 5,293,465 AGranted

Franking machine with digital printer

AssigneeNeopost Limited

InventorsCyrus Abumehdi, Raymond J. Herbert

Life of this patent

Estimating the term…

Loading patent…

Abstract

A franking machine is disclosed in which a digital printing device such as a thermal printer or ink jet printer is connected to accounting circuits of the franking machine so as to be controlled thereby to print franking impressions. In order to prevent unauthorised control of the printing device by application of external print signals, print data signals output by the accounting circuit are encrypted by logically combining the signals with pseudo random strings of binary bits. At the printing device the encrypted print data signals are decrypted by logically combining the encrypted print data signals with a corresponding pseudo random string of binary bits to provide print signals to control the printing device. Connections between the decryption circuit and the print head are protected from unauthorised access.

Claims16

Dependent claims

A franking machine including electronic accounting and control circuits and a digital printing device operable by print data signals comprising binary bits generated by the accounting and control circuits to print franking impressions including a representation of a postage charge means to transmit the print data signals from the accounting and control circuits to the digital printing device including encryption means at the accounting and control circuits comprising a first generator to generate a first pseudo random string of binary bits and means to logically combine successive bits of the first pseudo random string with bits of the print data signals to produce encrypted print data signals and decryption means at the printing device comprising a second generator to generate a second pseudo random string of binary bits corresponding to said first pseudo random string of binary bits and means to logically combine successive bits of the second pseudo random string of binary bits with bits of the encrypted print data signals to reproduce the bits of the print data signals to operate the printing device.

A franking machine including electronic accounting and control circuits and a digital printing device comprising a plurality of print elements;

said plurality of print elements being operable in each of a succession of print cycles by a string of print data binary bits corresponding to said respective print elements and generated by said accounting and control circuits to print in said succession of print cycles a franking impression including a representation of postage information;
transmission means to transmit said string of print data bits from said accounting and control circuits to said digital printing device including encryption means at the accounting and control circuits comprising a first generator to generate a first pseudo random string of binary bits corresponding respectively to said string of print data bits and first means to logically combine successive bits of the first pseudo random string with corresponding bits of said string of print data binary bits to produce a string of encrypted print data bits and decryption means at said printing device comprising a second generator to generate a second pseudo random string of binary bits corresponding to said first pseudo random string of binary bits and second means to combine successive bits of the second pseudo random string of binary bits with corresponding bits of said string of encrypted print bits thereby to reproduce said string of print data binary bits to operate said print elements of said printing device.

A franking machine including electronic accounting and control circuits and a digital printing device comprising a plurality of print elements;

said plurality of print elements being operable in each of a succession of print cycles by a like plurality of binary print data bits corresponding to said plurality of print elements and generated by said accounting and control circuits to print in said succession of print cycles a franking impression including a representation of postage information;
transmission means to transmit said print data bits from said accounting and control circuits to said digital printing device including encryption means at the accounting and control circuits comprising a first generator to generate a plurality of pseudo random first binary bits and first means to logically combine said pseudo random first binary bits respectively one with each of said print data binary bits to produce a plurality of encrypted print data bits and decryption means at said printing device comprising a second generator to generate a plurality of pseudo random second binary bits corresponding to said plurality of pseudo random first binary bits and second means to logically combine said pseudo random second binary bits respectively one with each of said encrypted print data bits thereby to reproduce said plurality of print data bits to operate said elements of said digital printing device.

Dependencies are inferred from the claim text.