Client Puzzle Protocol (CPP) is a computer
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...
for use in
Internet
The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
communication, whose goal is to make abuse of server resources infeasible. It is an implementation of a
proof-of-work system
Proof of work (also written as proof-of-work, an abbreviated PoW) is a form of Cryptography, cryptographic proof (truth), proof in which one party (the ''prover'') proves to others (the ''verifiers'') that a certain amount of a specific computatio ...
(PoW).
The idea of the CPP is to require all
clients connecting to a
server to correctly solve a
mathematical puzzle
Mathematical puzzles make up an integral part of recreational mathematics. They have specific rules, but they do not usually involve competition between two or more players. Instead, to solve such a puzzle, the solver must find a solution that sati ...
before establishing a connection, if the server is under attack. After solving the puzzle, the client would return the solution to the server, which the server would quickly verify, or reject and drop the connection. The puzzle is made simple and easily solvable but requires at least a minimal amount of computation on the client side. Legitimate users would experience just a negligible computational cost, but abuse would be deterred: those clients that try to simultaneously establish a large number of connections would be unable to do so because of the computational cost (time delay). This method holds promise in fighting some types of
spam
Spam most often refers to:
* Spam (food), a consumer brand product of canned processed pork of the Hormel Foods Corporation
* Spamming, unsolicited or undesired electronic messages
** Email spam, unsolicited, undesired, or illegal email messages
...
as well as other attacks like
denial-of-service.
See also
*
Computer security
Computer security (also cybersecurity, digital security, or information technology (IT) security) is a subdiscipline within the field of information security. It consists of the protection of computer software, systems and computer network, n ...
*
Intrusion-prevention system
*
Proof-of-work system
Proof of work (also written as proof-of-work, an abbreviated PoW) is a form of Cryptography, cryptographic proof (truth), proof in which one party (the ''prover'') proves to others (the ''verifiers'') that a certain amount of a specific computatio ...
*
Hashcash
*
Guided tour puzzle protocol
References
*{{cite book , first=Ari , last=Juels , first2=John , last2=Brainard , chapter=Client Puzzles: A Cryptographic Countermeasure Against Connection Depletion Attacks , editor-first=S. , editor-last=Kent , title=Proceedings of NDSS '99 (Networks and Distributed Security Systems) , pages=151–165 , year=1999 , chapter-url=http://www.arijuels.com/wp-content/uploads/2013/09/JB99.pdf
External links
RSA press release about client puzzlesClient Puzzles: A Cryptographic Countermeasure Against Connection Depletion AttacksNew Client Puzzle Outsourcing Techniques for DoS Resistance
Computer network security