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:
Jul. 18, 2000
Filed:
Jul. 28, 1997
Arnaldo Campinos, Rennes, FR;
Jean-Bernard Fischer, Rennes, FR;
Thomson multimedia, S.A., , FR;
Abstract
The invention relates to a conditional access system making it possible for a service provider to supply his services solely to users having acquired entitlements to these services. The services supplied by a service provider consist of an item scrambled by control words. To keep these control words secret, they are supplied in messages (MEC) after having been encrypted with an encryption algorithm with key K. According to the invention, one and the same message (MEC) contains the same control word (Cwi) encrypted several times, each encryption (E(Cwi)Kj) of the control word depending on a different encryption key (Kj). The invention applies to any type of conditional access system, be this system either of 'off-line' or 'on-line' type.