Treatment of the initial value in Time-Memory-Data Tradeoff attacks on stream ciphers

Orr Dunkelman, Nathan Keller

Research output: Contribution to journalArticlepeer-review


Time-Memory Tradeoff (TMTO) attacks on stream ciphers are a serious security threat and the resistance to this class of attacks is an important criterion in the design of a modern stream cipher. TMTO attacks are especially effective against stream ciphers where a variant of the TMTO attack can make use of multiple data to reduce the off-line and the on-line time complexities of the attack (given a fixed amount of memory). In this paper we present a new approach to TMTO attacks against stream ciphers using a publicly known initial value (IV): We suggest not to treat the IV as part of the secret key material (as done in current attacks), but rather to choose in advance some IVs and apply a TMTO attack to streams produced using these IVs. We show that while the obtained tradeoff curve is identical to the curve obtained by the current approach, the new technique allows to mount the TMTO attack in a larger variety of settings. For example, if both the secret key and the IV are of length n, it is possible to mount an attack with data, time, and memory complexities of 24 n / 5, while in the current approach, either the time complexity or the memory complexity is not less than 2n.

Original languageEnglish
Pages (from-to)133-137
Number of pages5
JournalInformation Processing Letters
Issue number5
StatePublished - 16 Aug 2008
Externally publishedYes

Bibliographical note

Funding Information:
* Corresponding author. E-mail addresses: (O. Dunkelman), (N. Keller). 1 This work was supported in part by the Concerted Research Action (GOA) Ambiorics 2005/11 of the Flemish Government and by the IAP Programme P6/26 BCRYPT of the Belgian State (Belgian Science Policy). 2 This author is supported by the Adams Fellowship Program of the Israel Academy of Sciences and Humanities.


  • Cryptography
  • Time-Memory Tradeoff attacks
  • Time-Memory-Data Tradeoff attacks

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Signal Processing
  • Information Systems
  • Computer Science Applications


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