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:
Dec. 17, 1996
Filed:
Jul. 15, 1994
Gideon A Yuval, Mercer Island, WA (US);
Michael Ernst, Redmond, WA (US);
Microsoft Corporation, Redmond, WA (US);
Abstract
A system for controlling unauthorized access to information distributed to users and, more particularly, for controlling unauthorized access to software distributed to users is provided. One method utilizing the system of the present invention enables the software to be encrypted using a single encryption key and to be decrypted using a multiplicity of 'decryption' keys, each of which is unique to a particular user. The 'decryption' keys are the products of numeric representations of identifying information relating to users and unique user keys generated using the numeric representations and a 'true' decryption key. Since each user receives a unique user key and both the numeric representation and the user key are generated using the identifying information, if the user reveals the numeric representation and the user key (or the product of the numeric representation and the user key), the numeric representation and the user key can be traced to the user who revealed them. Another method utilizing the system of the present invention introduces randomness or pseudo-randomness into the decryption scheme to provide an additional level of security to the scheme.