Unconditional Security of Cryptosystem: A Review and Outlook

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

Liu Yu

Quantum communication is a new interdisciplinary research field which combines the classical communication theories and quantum mechanics,and is the only theory,widely acknowledged by researchers worldwide,that can realize unconditionally secured communication.This essay analyzes the security weaknesses of the existing cryptosystems,reviews the concept of quantum cryptosystem,examines in details the complete process of the most typical quantum security key distribution protocol-the BB84 protocol-and analyzes its security.

Stefan Wolf

Yu‐Fang Chung, Zhen Yu Wu, Feipei Lai +1 more

Most cryptographic works these days have employed mathematical concepts to design cryptosystems and algorithms.Therefore, mathematical concepts have become critical in the designing of cryptosystems, and are generally used to analyze cryptosystems and protocols, supporting the allegation that the intended cryptosystem is secure.In earlier cryptosystems, most algorithms were based on either factorization or discrete logarithm problem.This system has an overtly simple mathematical background and so, requires extensive secondary index computation.Therefore, a securer method must be developed to protect system security and to optimize system efficiency.Quantum cryptography detects intrusion and wiretapping.In quantum mechanics, a wiretap is not external or passive, but the opposite-changing its entity according to the internal component of the system.The status of the system changes once a wiretap is detected.Therefore, only the designer of the system can determine the quantum status of the system; eavesdroppers can neither determine the quantum status nor duplicate the system.Since quantum cryptosystem can reach unconditional security, it actually guarantees secure communication.Accordingly, this study examines quantum cryptography and contributes to secure quantum cryptography.

Giles Brassard

S. N. Molotkov, S. S. Nazin

The problem of unconditional security of quantum cryptography (i.e. the security which is guaranteed by the fundamental laws of nature rather than by technical limitations) is one of the central points in quantum information theory. We propose a relativistic quantum cryptosystem and prove its unconditional security against any eavesdropping attempts. Relativistitic causality arguments allow to demonstrate the security of the system in a simple way. Since the proposed protocol does not empoly collective measurements and quantum codes, the cryptosystem can be experimentally realized with the present state-of-art in fiber optics technologies. The proposed cryptosystem employs only the individual measurements and classical codes and, in addition, the key distribution problem allows to postpone the choice of the state encoding scheme until after the states are already received instead of choosing it before sending the states into the communication channel (i.e. to employ a sort of "antedate" coding).