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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.:

US 7600255 B1

PDFFull Text
Date of Patent:
Oct. 06, 2009

Filed:

Apr. 14, 2004

Preventing network denial of service attacks using an accumulated proof-of-work approach

Applicant:

Mark Baugher, Portland, OR (US);

Inventor:

Mark Baugher, Portland, OR (US);

Assignee:

Cisco Technology, Inc., San Jose, CA (US);

Attorney:

Hickman Palermo Truong & Becker LLP

Primary Examiner:

Nasser G Moazzami

Assistant Examiner:

Oscar A Louie

Int. Cl.
CPC ...
G06F 7/04 (2006.01); G06F 17/30 (2006.01); G06F 7/58 (2006.01); G06F 15/16 (2006.01); G06F 12/00 (2006.01); G06F 12/14 (2006.01); G06F 13/00 (2006.01); G06F 11/00 (2006.01); G06F 12/16 (2006.01); G06F 15/18 (2006.01); G06F 15/173 (2006.01); G06F 15/177 (2006.01); G06K 9/00 (2006.01); G06K 19/00 (2006.01); H04L 9/32 (2006.01); H04L 9/00 (2006.01); H04L 1/00 (2006.01); H04L 12/26 (2006.01); G11C 7/00 (2006.01); G08B 23/00 (2006.01); H03M 1/68 (2006.01); H04K 1/00 (2006.01); H04K 3/00 (2006.01); H04N 7/16 (2006.01); B41K 3/38 (2006.01); G01R 31/08 (2006.01); G08C 15/00 (2006.01); H04J 1/16 (2006.01); H04J 3/14 (2006.01);
U.S. Cl.
CPC ...
Abstract

Accumulated proof-of-work approaches for protecting network resources against denial-of-service attacks are disclosed. A client computer or other requester is required to perform work, such as repeatedly hashing a message until a specified number of bits is zero, as a condition for accessing a resource. Proof of the work performed by a legitimate requester is accumulated across multiple requests, so that established users of a resource are not penalized when proof-of-work is used to prevent a denial of service attack. Requesters who cannot show accumulated work greater than a specified threshold are required to perform additional work. In certain embodiments, work may be accumulated only within a specified time window, and the threshold may vary according to resource capacity or loading. Proof-of-work values may be communicated between the user and the resource in cookies.

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