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:
Mar. 31, 2009
Filed:
Aug. 11, 2004
Serge Vaudenay, Crissier, CH;
Pascal Junod, Lausanne, CH;
Serge Vaudenay, Crissier, CH;
Pascal Junod, Lausanne, CH;
Nagravision SA, Cheseaux-sur-Lausanne, CH;
Abstract
Provided is a method to generate sub-keys based on a main key in a case in which, each sub-key gives no information to recover the main key. The method has the steps of obtaining a first value by applying to the main key a linear diversification by mixing the main key with a constant and applying to the first value a non-linear transformation. The non-linear transformation includes obtaining a second value by applying the first value to a substitution layer, obtaining a third value formed of N blocks of the same size by using a diffusion box of multi-permutation type based on the second value, obtaining the fourth value formed by blocks, obtaining the fifth value by applying to the fourth value a substitution layer, obtaining the sub-key by applying to the fifth value a symmetrical encryption module. The first value serves as the key input for this method.