THE TECHNOLOGY OF BUILDING A TWO-OPERAND FOUR-BIT OPERATION OF MINIMAL COMPLEXITY FOR STRICTLY SUSTAINABLE CRYPTOGRAPHIC CODING

Abstract

In the article were applied logical functions in the operation matrix cryptographic transformation of information based on addition modulo two for the protection of the confidential information resources. It was developed a construction technology of the two-operand four-bit operation of minimal complexity with a property of strictly sustainable cryptographic coding. This construction technology consists in the fact that pair-wise inverting of a certain number of digits is performed and a half of digits of the input information is inverted, while taking into account the limitations that only one digit can be inverted in each transposition of the digits. Such strictly sustainable cryptographic coding leads to a large uncertainty in the value of each bit of the uncoded message when attempting to decode the encoded message. The two-operand four-bit operation with the strictly sustainable cryptographic coding property is created on the basis of one-operand operations with their sequential addition modulo two. A complete set of one-operand four-bit operations of minimal complexity contains 42 operations depending on the number of transpositions (zero, one and two transpositions). For the construction of this two-operand four-bit operation of minimal complexity with the strictly sustainable cryptographic coding property, 16 four-bit operations were chosen, obtained from the basic four-bit operations by one transposition in which only one bit is inverted. The truth tables were constructed for a simplified operation model without taking into account the signals of the inversion of functions, and then a model of a generalized operation was constructed taking into account the inversion of functions. The proposed technology for constructing a two-operand four-bit operation of minimal complexity with the strictly sustainable cryptographic coding property is verified by creating one of the twooperand four-bit operations for stream encryption.