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:
Feb. 09, 2010
Filed:
Mar. 22, 2004
Andrew D. Birrell, Los Altos, CA (US);
Michael Burrows, Palo Alto, CA (US);
Edward Pearce Wobber, Menlo Park, CA (US);
Andrew D. Birrell, Los Altos, CA (US);
Michael Burrows, Palo Alto, CA (US);
Edward Pearce Wobber, Menlo Park, CA (US);
Microsoft Corporation, Redmond, WA (US);
Abstract
Methods and systems are provided for a cancellation server maintaining a database of identifiers of cryptographic puzzles. A cryptographic puzzle is created from a unique identifier and a timestamp, and is attached to an electronic mail message, along with the puzzle's solution. The recipient verifies that the solution is correct and that the timestamp is current, and further queries the cancellation server with the puzzle identifier. If the identifier does not exist in the database, then the recipient knows the received message is legitimate. If the identifier already appears in the database, the received message can be automatically removed from the recipient's computer.