US 7,321,737 B2
System for authenticating modules installed in machines, such as printing apparatus
Kevin Swann, St. Albans (United Kingdom); and Roger Huggins, Knebworth (United Kingdom)
Assigned to Xerox Corporation, Norwalk, Conn. (US)
Filed on Jun. 30, 2005, as Appl. No. 11/172,309.
Prior Publication US 2007/0003293 A1, Jan. 04, 2007
Int. Cl. G03G 15/00 (2006.01)
U.S. Cl. 399—12 18 Claims
OG exemplary drawing
 
1. A method of operating a machine, comprising:
installing into the machine a module having a first random number generator associated therewith;
incidental to installing the module, initiating a second random number generator associated with the machine;
each of the first random number generator and the second random number generator outputting a series of random numbers over time; and
at a predetermined time, checking that a random number recently output by the second random generator is of a predetermined relationship to a random number recently output by the first random number generator.