Division Zero (Div0). Copyright © 2011-2018

All rights reserved.

Client Puzzle Protocol (CPP)

30 Oct 2012

Client Puzzle Protocol (CPP) is a proof-of-concept, in the late 1990s and early 2000s, to defend against denial-of-service (DoS) attacks.

Clients connecting to a server need to solve a mathematical puzzle correctly before a connection is established. Although the puzzle requires negligible computation cost from the client end, it is able to slow down simultaneously establishment of large number of connections.


A simple but brilliant idea it may seems, it is not widely adopted as it requires the modification of the underlying transport protocol (i.e. TCP).


  • Client Puzzle Protocol, Wikipedia.

  • Client Puzzle: A Cryptographic Countermeasure Against Connection Depletion Attacks, Ari Juels and John Brainard.

  • RSA Laboratories Unveils Innovative Countermeasure To Recent “Denial of Service” Hacker Attacks, RSA Lab.











Share on Facebook
Share on Twitter
Please reload


September 5, 2017

Please reload

Please reload

RSS Feed