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Breaking substitution ciphers using a relaxation algorithm

Published:01 November 1979Publication History
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Abstract

Substitution ciphers are codes in which each letter of the alphabet has one fixed substitute, and the word divisions do not change. In this paper the problem of breaking substitution ciphers is represented as a probabilistic labeling problem. Every code letter is assigned probabilities of representing plaintext letters. These probabilities are updated in parallel for all code letters, using joint letter probabilities. Iterating the updating scheme results in improved estimates that finally lead to breaking the cipher. The method is applied successfully to two examples.

References

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  • Published in

    cover image Communications of the ACM
    Communications of the ACM  Volume 22, Issue 11
    Nov. 1979
    37 pages
    ISSN:0001-0782
    EISSN:1557-7317
    DOI:10.1145/359168
    Issue’s Table of Contents

    Copyright © 1979 ACM

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    Association for Computing Machinery

    New York, NY, United States

    Publication History

    • Published: 1 November 1979

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