On the concept of a e-perfect cipher | Prikladnaya Diskretnaya Matematika - Applied Discrete Mathematics. 2016. № 3(33). DOI: 10.17223/20710410/33/3

The generalizations of the perfect cipher concept are discussed. A cipher is called е-perfect if the maximum absolute value of the difference between the posterior and prior probabilities of a plaintext does not exceed е. Two constructions of е-perfect ciphers for a multitude of plaintexts with a minor limitation of their frequency characteristics are studied. The notion of е-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, е-perfectness and its analogues have much better proximity to perfectness.