Sending or Not-Sending Twin-Field Quantum Key Distribution with Flawed and Leaky Sources

Twin-field quantum key distribution (TF-QKD) and its variants can overcome the fundamental rate-distance limit of QKD which has been demonstrated in laboratory field while their physical implementations with side channels remains to be further researched. We find external modulation different intensity states through test, required those TF-QKD post-phase compensation, shows a channel frequency domain. Based on this, we propose complete undetected eavesdropping attack, named passive shift sending or not-sending (SNS) protocol given any difference between signal decoy domain extended other imperfections distinguishable states. analyze this attack by giving formula upper bound real secure rate comparing it lower secret under Alice Bob's estimation consideration actively odd-parity pairing (AOPP) method finite effects. The simulation results show that Eve get full information about bits without being detected at long distance. Our emphasize importance practical security source might provide valuable reference for implementation TF-QKD.