Paper 2004/136

CompChall: Addressing Password Guessing Attacks

Vipul Goyal, Virendra Kumar, Mayank Singh, Ajith Abraham, and Sugata Sanyal


Even though passwords are the most convenient means of authentication, they bring along themselves the threat of dictionary attacks. Dictionary attacks may be of two kinds: online and offline. While offline dictionary attacks are possible only if the adversary is able to collect data for a successful protocol execution by eavesdropping on the communication channel and can be successfully countered using public key cryptography, online dictionary attacks can be performed by anyone and there is no satisfactory solution to counter them. This paper presents a new authentication protocol which is called CompChall (computational challenge). The proposed protocol uses only one way hash functions as the building blocks and attempts to eliminate online dictionary attacks by implementing a challenge-response system. This challenge-response system is designed in a fashion that it does not pose any difficulty to a genuine user but is time consuming and computationally intensive for an adversary trying to launch a large number of login requests per unit time as in the case of an online dictionary attack. The protocol is stateless and thus less vulnerable to DoS (Denial of Service) attacks.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Information Assurance and Security Track, ITCC-2005, USA, IEEE Computer Society, April 2005
Contact author(s)
vipul goyal @ cse04 itbhu org
2006-12-30: last of 3 revisions
2004-06-06: received
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Creative Commons Attribution


      author = {Vipul Goyal and Virendra Kumar and Mayank Singh and Ajith Abraham and Sugata Sanyal},
      title = {CompChall: Addressing Password Guessing Attacks},
      howpublished = {Cryptology ePrint Archive, Paper 2004/136},
      year = {2004},
      note = {\url{}},
      url = {}
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