The selection of encryption keys for hydroacoustic communication channel
The most suitable algorithm for encryption in the hydroacoustic communication channel is the RC4 cipher. It allows to encrypt and decrypt information quickly and use keys with variable length. But even this algorithm needs to be improved. The main problem is the generation of efficient keys. They are usually formed by pseudo-random sequence generators (PRS) and it is important that these generators generate “pure” random sequences for the highest cipher strength. In addition, it should be noted that it may be necessary to change the size of the keys from 5 to 64 bytes, in depend of the distance between objects and the speed of their movement, and that will make it possibleto choose a key of either greater or lesser length. The second problem is the need for synchronization of sending and receiving messages, so a strict synchronization system is needed. The purpose of this work is consideration of possible ways to solve the first problem (creation of the necessary set of effective encryption keys). In order to obtain the best encryption that provides the highest level of protection for the transmitted information, a comparative analysis of the schemes of construction of PRS generators.was carried out. The analysis leads to the conclusionthat it is recommended to use the Fibonacci scheme to increase the strength of speech encryption algorithms. In addition, an assessment of the degree of influence on the characteristics of the PRS generators of the number of generating polynomials was made for the Fibonacci scheme. The analysis of residual intelligibility showed that not a single word can be parsed in the encrypted file, therefore residual intelligibility is zero, which confirms the effectiveness of the proposed method of information security.