Are There Enough Decoy States to Ensure Key Secrecy in Quantum Cryptography?

The decoy state method has been proposed to detect a photon number splitting (PNS) attack. Today, the decoy state method is considered to be an almost universal method for proving the secrecy of quantum cryptography protocols and calculating the length of a secret key. In this paper, it is shown tha...

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Bibliographic Details
Published in:Journal of experimental and theoretical physics 2019-04, Vol.128 (4), p.544-551
Main Authors: Molotkov, S. N., Kravtsov, K. S., Ryzhkin, M. I.
Format: Article
Language:English
Subjects:
Atoms
Beam splitters
BEAM SPLITTING
Change detection
Classical and Quantum Gravitation
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Cryptography
Data encryption
DETECTION
Elementary Particles
Molecules
Optics
Particle and Nuclear Physics
PHOTONS
Physics
Physics and Astronomy
QUANTUM CRYPTOGRAPHY
Quantum Field Theory
Relativity Theory
Solid State Physics
Splitting
STATISTICS
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Summary:The decoy state method has been proposed to detect a photon number splitting (PNS) attack. Today, the decoy state method is considered to be an almost universal method for proving the secrecy of quantum cryptography protocols and calculating the length of a secret key. In this paper, it is shown that there exist attacks, for example, a beam splitting (BS) attack, to which the decoy state method turns out to be insensitive. The decoy state method is oriented to the detection of changes in the photocount statistics of information states and decoy states under a PNS attack. Under a BS attack, the photocount statistics is not changed. As a result, the decoy state method significantly overestimates the length of the key. Thus, the decoy state method is not a universal method that allows the detection of various attacks. Apparently, due to a large number of publications on the decoy state method, a widespread opinion has been formed that this method is universal. This fact has led to attempts to adopt this method as an international standard in quantum cryptography, which is clearly premature.
ISSN:1063-7761
1090-6509
DOI:10.1134/S1063776119030105