Kozlovska S. Methods of synthesis of symmetric operations groups for stream encryption

The thesis is devoted to the improvement of the confidential information’s stream ciphering systems at the expense of increasing the stability and variability of transformation basing on the additional use of two-operand two-bit operations’ groups synthesized on the bases of modulo-2 and modulo-4 addition. For this purpose, a method for constructing and investigating the two-operand operations of cryptographic transformation based on the results of a calculation experiment, through formalization, classification and mathematical transformation has been developed. The synthesizing methods of symmetric two-bit two-operand stream ciphering operations’ groups based on the results of a calculation experiment are developed using the implementation results of the developed technology and the table representation of the group’s classification of the one-operand two-bit operations of cryptographic transformation, as well as establishing the new previously unknown relationships between one-operand and two-operand operations. The method of increasing the stability and reliability of stream ciphering basing on the additional application of the synthesized groups of symmetric two-operand operations of cryptographic information transformation has been improved, which has provided increased stability and variation of stream ciphering.