π¬ Quantum security protocol found vulnerable to attack
A recent protocol for Quantum Secure Direct Communication (QSDC) was shown to be vulnerable through cryptanalysis. This finding was made by researchers regarding the CICBQSDC scheme developed by Cai et al. The protocol relied on four-particle cluster states and was published on August 31, 2026. The attack utilized a quantum Trojan-horse method, allowing the controller to fully recover all four secret message bits. This proves that the unconditional security claim of the original protocol is flawed due to its idealized assumptions π§.