This article is cited in 6 papers

Mathematical Methods of Cryptography

On the concept of a $\varepsilon$-perfect cipher

A. Yu. Zubov

Lomonosov Moscow State University, Moscow, Russia

Abstract: The generalizations of the perfect cipher concept are discussed. A cipher is called $\varepsilon$-perfect if the maximum absolute value of the difference between the posterior and prior probabilities of a plaintext does not exceed $\varepsilon$. Two constructions of $\varepsilon$-perfect ciphers for a multitude of plaintexts with a minor limitation of their frequency characteristics are studied. The notion of $\varepsilon$-perfect cipher is one of the possible approximations to the notion of a perfect cipher. For studied constructions of ciphers, it is shown that, in comparison with the other such approximations, $\varepsilon$-perfectness and its analogues have much better proximity to perfectness.

Keywords: perfect cipher, $\varepsilon$-perfect cipher.

UDC: 519.7

DOI: 10.17223/20710410/33/3

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