Translated by Yu. Kornienko
In this paper, we consider some probability-theoretical models of information distortion at the message level. The checksum (CS) distributions typical of TCP-type protocols are investigated. As an addition operator in the CS, bitwise coordinate addition and binary addition with carryover are considered. For the distortion models described, asymptotic estimates of CS error probabilities are obtained at a small distortion probability. These asymptotic estimates can be useful for messages with long segments.