Improvements on Efficient Controlled Semi‐Quantum Secret Sharing With Entangled States

Semi‐quantum secret sharing represents a significant area in quantum cryptography, offering the advantage of not requiring all participants to be fully quantum‐capable. Recently, Houshmand et al. (Opt. Quant. Electron. 2024, 56(5), 759) proposed a controlled semi‐quantum secret sharing protocol based on entangled states and claimed it was secure. However, the results of our analysis indicate that its security check is flawed and that the secret can be recovered if collaborates with any single other classical user. Accordingly, we propose an improved protocol that rectifies the flaws and resists not only the aforementioned attack, but also attacks initiated by up to dishonest users. In addition, our analysis of an existing denial‐of‐service attack shows that this attack cannot induce classical users to recover incorrect secrets. Consequently, no security check is necessary for this attack.