Cryptanalysis of efficient controlled semi-quantum secret sharing protocol with entangled state.

Quantum secret sharing is a basic quantum cryptographic primitive, which plays an important role in robust key management and secure multiparty computation etc. In this work, we give a cryptanalysis of efficient controlled semi-quantum secret sharing protocol with entangled states proposed recently, which shows that the controller can recover the secret if he cooperates with any one participant. Furthermore, an external opponent can make participants recover a false secret without being detected by a special denial-of-service attack. Therefore, this protocol does not satisfy the security requirement that any unauthorized set can gain access to no information on the secret and cannot guarantee its correctness.