Epistemic algorithms are instructions and rules based on knowledge of agents. These algorithms by individual or group knowledge of agents make decisions about future behavior of systems. Epistemic gossip protocols is one of these algorithms. They are used to for spreading secrets among nodes in a network. According to individual knowledge of each node they decide who calls whom in each step. In security problems epistemic algorithms are used to detect the safety of protocols. Some epistemic notions like ignorance and contingency are used in formalization of security problems. In the thesis we study these epistemic algorithms