Multiphoton and Side-Channel Attacks in Mistrustful Quantum Cryptography

Mistrustful cryptography includes important tasks like bit commitment, oblivious transfer, coin flipping, secure computations, position authentication, digital signatures and unforgeable tokens. Practical quantum implementations presently use photonic setups. In many such implementations, Alice sends photon pulses encoding states Bob chooses measurements on these states. practice, generally uses single threshold detectors, which cannot distinguish the number of photons in detected pulses. Also, losses other imperfections require to report Thus, malicious can send track multiphoton thereby gain information about Bob's measurement choices, violating protocols' security. Here, we provide a theoretical framework for analysing attacks, present known new attacks. We illustrate power attacks with an experiment, study their application earlier experimental demonstrations mistrustful cryptography. analyse countermeasures based selective reporting prove them inadequate. also discuss side-channel where controls further degrees freedom or physical systems.