Three Party Quantum Authenticated Key Distribution Protocol Using Superposition States

This paper presents a Quantum authenticated key distribution protocol that can perform key distribution and also ensure that the participants of the communication are authentic, both implicitly and explicitly. This protocol provides new directions in Classical cryptography and Quantum cryptography. The Participants of the protocol trust the third party regarding the authentication part only. Thus the proposed protocol will be preferable for network systems which deal with highly sensitive information, such as military, hospitals, research facilities. Our protocol utilizes polarized photons in superposition states for authentication and key distribution which provides high security against many attacks. Keywords— Quantum Cryptography, Superposition states, Authentication, Key distribution. 1.INTRODUCTION Cryptography is the art of secret writing. The main goal of cryptography is to enable secure communication in a hostile environoment: two parties , say Alice and Bob, want to safely communicate over a network occupied by an adversary. Usually, Alice and Bob will want to ensure the privacy and authenticity of the data they send to each other; to this end, they will encrypt and authenticate their transmissions. But before Alice and Bob can use these tools they will need to have keys. Indeed, without keys, cryptography simply cannot get off the ground. The purpose of key distribution is for two users “Alice” and “Bob” , who share no secret information initially, to agree on a random key, which remains secret from an adversary “Eve”, who eavesdrops on their communications. In classical cryptography, it is taken for granted that communications can always be passively monitored , so that the eavesdropper learns their entire contents, without the sender or receiver being aware that any eavesdropping has taken place. By contrast, when information is encoded in elementary quantum systems such as single photons, it becomes possible to produce a communications channel whose transmissions cannot in principle be reliably read or copied by an eavesdropper . The eavesdropper cannot even gain partial information about such a transmission without disturbing it in a random and uncontrollable way likely to be detected by the channel’s legitimate users [1]. Now , it has been established that Quantum Key Distribution has the potential of absolutely secure communication that cannot be compromised by any eavesdropping technique. At the same time, the interceptor Eve can easily mount a “man-in-the-middle” attack, wherein, both the quantum & the public channels are cut and subsequently Eve communicates to Alice masquerading as Bob & to Bob, pretending to be Alice. The interceptor would thus share two independent keys with the two legitimate parties and have complete control over any encrypted information that the sender and the receiver might want to send to each other. The only way to offset this attack would be to somehow incorporate an Authentication mechanism into the whole system. The combination of Authentication mechanism and Quantum key distribution is referred to as the Quantum authenticated key exchange protocol. Many quantum cryptographic schemes have been proposed for the last two decades. Particularly, Quantum key distribution protocols [2] [3] [4] [5] [6] have been intensly researched [7] and realized in commercial applications [8] [9]. The Quantum key distribution provides unbreakable security and allows two parties to share random number secretly and use it as a secret key for a classical encryption scheme. Many Quantum authentication protocols are also proposed [10] [11] [12] [13]. Recently, a three-party quantum authenticated key distribution protocol (QAKD) has been proposed [14]. This three-party QAKD is immune to the man-in-the-middle attack, K Sathi Reddy et al, Int. J. Comp. Tech. Appl. , Vol 2 (5), 1589-1594 IJCTA | SEPT-OCT 2011 Available online@www.ijcta. com 1589 ISSN:2229-6093