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. 07, 1999
Filed:
Nov. 22, 1995
Hiroshi Yasukawa, Tokyo, JP;
Takashi Kurosawa, Tokyo, JP;
Microsoft Corporation, Redmond, WA (US);
Abstract
To facilitate protected distribution of digital data files, the files are segmented, and each segment (e.g. disk sector) is encrypted separately. Some segments can be left unencrypted, speeding access since less decryption is required. Different segments can utilize different encryption techniques, increasing protection against unauthorized decryption. A table stored in association with the encrypted data provides authorized users with data identifying the encrypted segments, and the form of encryption used. Decryption is accomplished with a layered set of operating system software that operates in conjunction with said table. Specialized APIs aren't used; applications programs are provided with unencrypted data using conventional APIs. Internal interfaces, invisible to the APIS, intercept normal processing calls (e.g READs) and direct them to internal decryption software that returns decrypted data back to the APIs.