Journal of the Korean Physical Society
Cryptanalysis of a multi-user quantum network system and quantum communication using χ-type entangled states
Gan Gao
Abstract
A quantum secure direct communication and quantum key distribution(QSDC-QKD) protocol based on χ-type entangled states was recently proposed by Hong et al. [J. Korean Phys. Soc. 61 , 1 (2012)]. By analyzing the protocol, we find that it is not secure; that is, the eavesdropper can eavesdrop on half of Bob’s secret messages and half of Alice’s secret keys without introducing any error.