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Journal of Experimental and Theoretical Physics Letters

On geometrically uniform states in quantum cryptography

S. N. Molotkov

Published May 1, 2012• 5 citations
Publisher

Abstract

A family of quantum key distribution protocols based on geometrically uniform states of laser radiation has been proposed. Their cryptographic strength against a unitary attack, a coherent-state-splitting attack, and an unambiguous measurement attack has been analyzed. A certain protocol can be chosen automatically depending on the parameters of a system and the required length of a communication channel.

DOI
10.1134/s0021364012060070

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Comment on “Practical quantum key distribution with geometrically uniform states”

Dmitry Anatolevich Kronberg

In a recent paper, Kravtsov and Molotkov [Phys. Rev. A 100, 042329 (2019)] propose a quantum key distribution protocol and claim ``the protocol security is analyzed by an explicit construction of the most optimal unitary attack'' and ``we provide an extensive security analysis of the proposed protocol by considering a general symmetric unitary attack, and give succinct relations for the asymptotic secret key rate in the case of $N=8$.'' We show that these claims are erroneous and propose two attacks which are more effective than the attacks considered in the paper of Kravtsov and Molotkov.

Physical Review A•Aug 3, 2021•3 citations
A family of quantum key distribution protocols based on geometrically uniform states of laser radiation has been proposed. Their cryptographic strength against a unitary attack, a coherent-state-splitting attack, and an unambiguous measurement attack has been analyzed. A certain protocol can be chosen automatically depending on the parameters of a system and the required length of a communication channel.
It is shown that the quantum cryptography protocol on geometrically uniform coherent states, which uses the restriction for unambiguous discrimination of a set of symmetric coherent states and allows resisting an unambiguous state discrimination attack (USD attack), is not secure to a number of other attacks. The key length formula from the work of S.N. Molotkov [ JETP Lett. , 101 (8), 579 (2015) ] and the key generation rate for a number of constructive attacks of the eavesdropper are compared and it is shown that the key generation rate in this work is significantly overestimated. This leads to the fact that the distributed key is not secret.
Abstract The quantum key distribution protocol utilizing 8 geometrically uniform coherent states is considered. We analyze its security against a generalized photon-number-splitting attack. This protocol allows for several basis configurations, and we demonstrate that one of these configurations is more vulnerable. We also use the previously described methods for attack improvement, namely, modification of observable’s coefficients and using extra photon as assistance for increasing success probability.
In this paper we propose a practical quantum key distribution protocol based on geometrically uniform states and a standard decoy state technique. The protocol extends the ideas used in SARG04 to the limit where the core quantum communication is secure against unambiguous state discrimination and provides some level of inherent resistance to photon number splitting attacks. An additional decoy state overlay ensures its conformity to the conventional security requirements. The protocol security is analyzed by an explicit construction of the most optimal unitary attack, which is known to reach the tight security bound in the case of BB84.
Abstract Quantum key distribution systems are open systems in the sense that in addition to attacking quantum states in the quantum communication channel, the eavesdropper can obtain additional information about the transmitted key using passive radiation detection of the transmitting and receiving stations, as well as active probing of the state of the equipment through a fiber communication line. In this paper, we consider the cryptographic robustness of a quantum cryptography system that uses a protocol with phase coding based on strongly weakened coherent geometrically uniform states. Non-strict single-photon information states, as well as information leakage through side channels, are taken into account by the generalized Decoy State method, taking into account joint collective measurements of information quantum states and quantum states in side channels. An estimate of the secret key length is obtained, which is expressed only in terms of the observed values at the receiving station and the parameters of quantum states in the side channels.
A new family of two-parameter quantum key distribution protocols is discussed where eavesdropping is detected by using two parameters: bit error rate Q and photon count rate q in control time slots. When a single-photon source is used and mutually orthogonal states are prepared in each basis, the protocol’s maximum tolerable error rate for secure key distribution is the highest, reaching a theoretical upper limit of 50%. When the signal states emitted by the source of attenuated laser light include multiphoton coherent states, the protocol also guarantees secure key distribution over the longest distance as compared to other quantum cryptography systems, up to the channel length for which the channel losses are sufficiently high that all five-photon pulses can be blocked by an eavesdropper.
In a recent paper, Kravtsov and Molotkov [Phys. Rev. A 100, 042329 (2019)] propose a quantum key distribution protocol and claim ``the protocol security is analyzed by an explicit construction of the most optimal unitary attack'' and ``we provide an extensive security analysis of the proposed protocol by considering a general symmetric unitary attack, and give succinct relations for the asymptotic secret key rate in the case of N=8N=8N=8.'' We show that these claims are erroneous and propose two attacks which are more effective than the attacks considered in the paper of Kravtsov and Molotkov.