Abstarct: Nowadays, transmission information between Alice and Bob, by method of quantum mechanics is focus of attention of scientists and researchers. In this way, trying for the most of security is very important. The first protocol, so called BB84, baxsed on the fundamental quantum feature: incompatibility of measurements of quantum non-computing observables. So, following security of transmission information in systems that they have many eavesdroppers, we receive to below results. In this thesis, we use another feature of quantum world- contextuality that manifested in famous Kochen-Specker paradox, and we increasing security of system, even if they do not trust devices. This paradox includes families of bipartite probability distributions which locally exhibit the Kochen-Specker paradox conditions and, in addition, exhibit a new Bell's inequality by using of principle information causality, that it has correlations stranger than quantum correlations. After all by using violation it, we gain an interval for considering about existing or not existing eavesdropper. In addition, after computing threshold noise, we obtain the rate of secure key.