On the Key Search Complexity in Quantum Cryptography with Strong Information-Theoretic Authentication

The stability of quantum key distribution systems is based not only on the detection of attacks on quantum states, which is guaranteed by the fundamental quantum theory laws, but also on ensuring the integrity of classical messages transmitted through an auxiliary classical communication channel. To detect attacks on the classic communication channel, the authentication procedure is used. Information-theoretic authentication guarantees the detection of attacks on the classical communication channel regardless of the computational and technical capabilities of an eavesdropper, including the quantum computer. The fundamental quantum cryptographic relationship between the abstract criterion of the robustness of quantum key distribution systems with theoretical-information authentication and the quantum key search complexity has been determined for the first time using simple means.