The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 01, 1996
Filed:
Feb. 21, 1995
Ronny P de Bruijn, St. Jansteen, NL;
Leonardus A van Weele, Terneuzen, NL;
Marc L Verboven, Nazareth, BE;
Roger R Vermeire, Terneuzen, NL;
Oscar E Schulze, Midland, MI (US);
Brian G Bell, Midland, MI (US);
Dale H Schultz, Midland, MI (US);
The Dow Chemical Company, Midland, MI (US);
Abstract
A secure front-end communication system which couples a plurality of actively redundant process control computers to a computer network. The system includes a front end computer which is capable of establishing time limited communication contracts with one or more computer entity on the computer network. Each time limited communication contract is based upon an acceptable response to the transmission of an unpredicable signal from the front end computer, such as an encrypted transformation of a psuedo-random number generated by the front end computer. A security table is used to identify the network entities that are permitted to send write command messages to the process control computers to which the front end computer is connected. The front end computer also includes at least one permissive table which is used to determined whether a write command message from the network entity should be transmitted to the process control computer for which the message was intended.