A quantum scheme for attack on a phase-time encoded quantum cryptography protocol

The main property of quantum cryptography is the ability to rigorously prove security against any attack. However, any security proof is complex and may contain errors. Incompleteness of the security proof creates a risk of vulnerability, i.e., a situation in which the eavesdropper has full or partial knowledge of the cryptographic key. In this paper, we propose a quantum attack scheme against a two-parameter quantum cryptography protocol with phase-time coding that demonstrates its vulnerability. It is shown that the constructed attack is relatively simple and requires only three additional qubits. The errors in the security proof that made the constructed attack possible are discussed.