Shannon impossibility, revisited

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In this note we revisit the famous result of Shannon [Sha49] stating that any encryption scheme with perfect security against computationally unbounded attackers must have a secret key as long as the message. This result motivated the introduction of modern encryption schemes, which are secure only against a computationally bounded attacker, and allow some small (negligible) advantage to such an attacker. It is a well known folklore that both such relaxations - limiting the power of the attacker and allowing for some small advantage - are necessary to overcome Shannon's result. To our surprise, we could not find a clean and well documented proof of this folklore belief. (In fact, two proofs are required, each showing that only one of the two relaxations above is not sufficient.) Most proofs we saw either made some limiting assumptions (e.g., encryption is deterministic), or proved a much more complicated statement (e.g., beating Shannon's bound implies the existence of one-way functions [IL89].)

Original languageEnglish (US)
Title of host publicationInformation Theoretic Security - 6th International Conference, ICITS 2012, Proceedings
Number of pages11
StatePublished - 2012
Event6th International Conference on Information Theoretic Security, ICITS 2012 - Montreal, QC, Canada
Duration: Aug 15 2012Aug 17 2012

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume7412 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other6th International Conference on Information Theoretic Security, ICITS 2012
CityMontreal, QC

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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