Dual-workfactor encrypted key exchange: efficiently preventing password chaining and dictionary attacks

  • Authors:
  • Barry Jaspan

  • Affiliations:
  • Independent consultant, Belmont, MA

  • Venue:
  • SSYM'96 Proceedings of the 6th conference on USENIX Security Symposium, Focusing on Applications of Cryptography - Volume 6
  • Year:
  • 1996

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Abstract

Password-based key-server protocols are susceptible to password chaining attacks, in which an enemy uses knowledge of a user's current password to learn all future passwords. As a result, the exposure of a single password effectively compromises all future communications by that user. The same protocols also tend to be vulnerable to dictionary attacks against user passwords. Bellovin and Merrit[1] presented a hybrid of symmetric- and public-key cryptography called Encrypted Key Exchange (EKE) that cleanly solves the dictionary attack problem. This paper presents an extension of their ideas called dual-workfactor encrypted key exchange that preserves EKE's strength against dictionary attacks but also efficiently prevents passive password-chaining attacks.