A closed system meter that secures the link between the accounting device and
utilizing a Linear Feedback Shift Register (LFSR) based stream encryption is provided.
The accounting device includes an LFSR that comprises a plurality of stages, with
one or more taps that are passed through a logic gate to provide a "feedback" signal
to the input of the LFSR, to generate a pseudo-random pattern output. Preferably,
a Shrinking Key Generator (SKG) is utilized to further ensure privacy of the data.
The output data from the accounting unit is encrypted utilizing the output from
the LFSR and sent to the printing device. The printing device includes a similar
LFSR, which is utilized to decrypt the output data from the accounting unit and