Electrical computers and digital processing systems: multicomput – Computer network managing – Computer network access regulating
Reexamination Certificate
2005-09-13
2005-09-13
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: multicomput
Computer network managing
Computer network access regulating
C709S227000, C713S152000
Reexamination Certificate
active
06944663
ABSTRACT:
One embodiment of the present invention provides a system that protects a server against denial-of-service attacks. During operation, the server receives a request for service from a client. Note that the client can be distinguished from other clients, for example, by its source IP address. In response to this request, the server sends a random number, y, and an identifier, id1, to the client, and allows the client to compute a preimage, x, such that y=h(x). Upon receiving an answer from the client including the preimage x and an identifier, id2, the server verifies that the identifier, id1, sent to the client matches the identifier, id2, received from the client. If the identifiers match, the server computes h(x), and compares h(x) against y. If h(x)=y, the server performs the requested service for the client. In this way, the server avoids computing h(x) until the server receives the answer with a matching identifier.
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Publication entitled “Using Client Puzzles to Protect TLS,” by Drew Dean and Adam Stublefield, proceedings of the 10thUsenic Security Symposium, Washington, D.C., USA, pp. 1-8, Aug. 2001.
Guttman Erik
Schuba Christoph L.
Lim Krisna
Park Vaughan & Fleming LLP
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