Attack on Quantum Key Distribution: Joint Unambiguous Measurements of Probe States and the PNS Attack on Information Statesстатья
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Дата последнего поиска статьи во внешних источниках: 16 декабря 2020 г.
Аннотация:A new attack on the quantum key distribution is proposed involving joint collective unambiguous measurementsof reflected probe states from an intensity modulator and photon number splitting (PNS) measurements,i.e., nondestructive measurements of the number of information photons in the quantum communicationchannel. This attack does not change the relative statistics of photocounts of states with different numbersof photons, does not lead to errors on the receiver side, and, thereby, is not detected by any of knownmethods, including the modified decoy state method. The attack results only in additional losses in the communicationchannel, which are not “controlled” by the decoy state method. The dependence of introducedlosses on the intensity of reflected probe states is estimated. The critical level of losses depends on a particularphysical implementation of the quantum cryptography system, which determines the upper bound of theintensity of reflected probe states. The knowledge of this bound is fundamentally necessary to ensure thesecurity of keys. The fact that the attack does not lead to errors on the receiver side and does not change therelative statistics of photocounts but only results in additional losses, which depend on the intensity accordingto the distinguishability of reflected probe states, does not mean that this attack transforms quantum cryptographysystems from the type of cryptographic systems where the security of keys is guaranteed by fundamentalquantum mechanical laws to the type of systems where this security is guaranteed by technical restrictions.Even in the presence of side channels of information leakage, the security of keys is still guaranteed by fundamentalquantum mechanical restrictions on the distinguishability of states. A low level of distinguishability(“intensity”) of quantum states in side channels is naturally reached by technical tools.