Abstarct: Quantum cryptography has attracted widespread attention as it is ultimately secure by using physics's laws and does not require computational and mathematical complexity unlike its classical counterparts. Quantum key distribution (QKD) is one of the most important applications of quantum cryptography. In QKD, two distant people (like Alice & Bob) can share a secret key with each other to use it further as a key of a classical cyphertext. From the first QKD protocol (BB84) to recent protocols which presented in last few years, all of them were baxsed on transmitting signal particles through a quantum channel. In 2009 Tae Gon Noh presented a novel QKD protocol by using the idea of "Interaction free measurement" (N09). In fact his protocol is entirely different from all previous QKD protocols, because the sifted key in N09 is just created by selecting the events which the photons have not actually traveled through the quantum channel. Thus the eavesdropper could not access those photons. Due to this advantage, N09 is very attractive from the security aspect. However the efficiency of the N09 is not satisfying. In this thesis, first the history of classical cryptography is mentioned. Then, after an introduction about Quantum information theory, the processes of QKD protocols is indicated. We have also mentioned three important QKD protocols and study their security. At the end we have investigated verify N09 protocol and its security in details.