An unconditionally secure protocol for quantum cryptography

Yu‐Fang Chung, Zhen Yu Wu, Tzer‐Shyong Chen

Subhash C. Kak

Aysajan Abidin

Authentication is an indispensable part of Quantum Cryptography, which is an unconditionally secure key distribution technique based on the laws of nature. Without proper authentication, Quantum Cryptography is vulnerable to “man-in-the-middle” attacks. Therefore, to guarantee unconditional security of any Quantum Cryptographic protocols, the authentication used must also be unconditionally secure. The standard in Quantum Cryptography is to use theWegman-Carter authentication, which is unconditionally secure and is based on the idea of universal hashing. In this thesis, we first investigate properties of a Strongly Universal hash function family to facilitate understanding the properties of (classical) authentication used in Quantum Cryptography. Then, we study vulnerabilities of a recently proposed authentication protocol intended to rule out a "man-in-the-middle" attack on Quantum Cryptography. Here, we point out that the proposed authentication primitive is not secure when used in a generic Quantum Cryptographic protocol. Lastly, we estimate the lifetime of authentication using encrypted tags when the encryption key is partially known. Under simplifying assumptions, we derive that the lifetime is linearly dependent on the length of the authentication key. Experimental results that support the theoretical results are also presented.

Yi Liu, Xingtong Liu, Jian Wang +2 more

Electronic payment protocols play a vital role in electronic commerce to ensure the security of transaction process. Current electronic payment protocols based on complex mathematical problems will be vulnerable facing a quantum computer. In order to enhance the security against quantum computers, quantum cryptography is introduced into electronic payment protocols. Although the quantum cryptography is claimed to be unconditionally secure, Logical defects are still likely to cause serious problems. We introduced formal analysis to verify the security of electronic payment protocols based on quantum cryptography. Formal analysis methods can discover the vulnerabilities of protocols and help to improve the security of protocols. In this paper, we analyze an electronic payment protocol based on quantum cryptography and the result shows that the protocol is not secure even adopting unconditionally secure quantum cryptography. We found that both the accountability and fairness of the original protocol are not satisfied. Then we proposed an improved protocol to meet the requirement of accountability and fairness and verified it through formal analysis method.

Anindita Banerjee

Dominic Mayers

The claim of quantum cryptography has always been that it can provide protocols that are unconditionally secure, that is, for which the security does not depend on any restriction on the time, space, or technology available to the cheaters. We show that this claim does not hold for any quantum bit commitment protocol. Since many cryptographic tasks use bit commitment as a basic primitive, this result implies a severe setback for quantum cryptography. The model used encompasses all reasonable implementations of quantum bit commitment protocols in which the participants have not met before, including those that make use of the theory of special relativity.