Abstract—A mathematical model has been developed for the computational core of the decision support system taken in the course of ensuring information security of exchange sessions for the sale and purchase of digital cryptocurrencies. The model contributes to making rational decisions to ensure the information security of players who may face the threat of phishing attacks against them. The model was developed on the basis of an infinite antagonistic game and is designed to find the optimal strategies for players. The solution of such a problem contributes to the analytical search not only for the value of the game, but also makes it possible to find the characteristics of the risk degree of achieving the goal by the players when they use optimal mixed strategies. The described solution contributes to the analysis of the situation with counteraction to the party attacking with the help of phishing the participant of the trading session for buying and selling digital cryptocurrencies. Computational experiments were carried out using the Anaconda distribution kit. The results obtained will be useful for analysts dealing with information security issues of trading platforms, specializing in the purchase and sale of digital cryptocurrencies, and counteracting the threats phishing attacks. During research, three specific zones in the resource space have been identified: “Safe Zone”, “Strategic Parity Zone”, and “Critical Risk Zone”. Mathematically proven, the “Safe Zone” of cryptocurrency exchange is not constant. It deforms nonlinearly as market trends change. The obtained results give informational security analysts a tool for the flexible redistribution of defense budgets during periods of high market volatility.
 
Keywords—endless antagonistic game, optimal strategy, phishing attack, trading session, digital cryptocurrency


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