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arXiv:0806.1778 · AIP conference proceedings

Proposal of an eavesdropping experiment for BB84 QKD protocol with 1→3 phase-covariant quantum doner

Yuta Okubo, Francesco Buscemi, Akihisa Tomita, Alexander Lvovsky

Published Jan 1, 2009• 2 citations
arXivHTMLPDF

Abstract

We propose an experimental implementation of a particular attack against the BB84 quantum key distribution protocol, utilizing a 1→3 asymmetric phase‐covariant quantum cloning. Our eavesdropping strategy is numerically optimized to extract the information about the input state. The proposed cloning circuit is easily implementable with linear optics and its performances turn out to be well close to the optimum attack.

DOI
10.1063/1.3131347

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We propose an experimental implementation of a particular attack against the BB84 quantum key distribution protocol, utilizing a 1→3 asymmetric phase‐covariant quantum cloning. Our eavesdropping strategy is numerically optimized to extract the information about the input state. The proposed cloning circuit is easily implementable with linear optics and its performances turn out to be well close to the optimum attack.
Abstract Passive light-source side channel in quantum key distribution (QKD) provides additional information to an eavesdropper via various non-operational degrees of freedom of the optical signal. The currently known explicit eavesdropping strategies aimed at additional information gain from the passive light-source side channel were limited to the attack on the side channel and the operational degree of freedom separately. As a result, their efficiency is far from being optimal. Here we provide the joint eavesdropping strategy on both operational degree of freedom and the passive light-source side channel of the generic form, and develop a method to calculate the corresponding secret key rate. In particular, we use the optimal phase-covariant cloning of the signal photon state followed by a joint collective measurement of the side channel and the operational degree of freedom. To estimate security under the explicit attack strategy, we develop an ‘‘effective error’’ method and demonstrate it on the BB84 protocol with decoy states. Our work extends the practical analysis of QKD protocols with the light-source side channels and can be used as a tool for the analysis of realistic eavesdropping methods.
We describe a nuclear magnetic resonance (NMR) experiment which implements an efficient one-to-two qubit phase-covariant cloning machine(QPCCM). In the experiment we have achieved remarkably high fidelities of cloning, 0.848 and 0.844 respectively for the original and the blank qubit. This experimental value is close to the optimal theoretical value of 0.854. We have also demonstrated how to use our phase-covariant cloning machine for quantum simulations of bit by bit eavesdropping in the four-state quantum key distribution protocol.
Quantum Key Distribution (QKD) provides an innovative approach for secure communication by utilizing the principles of quantum mechanics. Among various QKD protocols, the BB84 protocol remains the most widely studied and implemented due to its simplicity and theoretical security guarantees. However, practical implementations of BB84 are vulnerable to several eavesdropping attacks and channel imperfections. This paper presents a comprehensive study on the detection and analysis of eavesdropping attacks in the BB84 protocol. The work focuses on common attacks such as intercept-resend attack, photon-number splitting attack, Trojan horse attack, and phase-covariant cloning attack. The effect of these attacks on Quantum Bit Error Rate (QBER) is analyzed in detail. Simulation-based observations are discussed to demonstrate how QBER increases under malicious interference. The study further explores statistical methods for detecting eavesdropping and examines practical countermeasures including decoy states, privacy amplification, and error correction techniques. The paper concludes that BB84 remains robust against eavesdropping when proper detection and mitigation mechanisms are employed.
Abstract Various imperfections of the hardware in quantum key distribution (QKD) lead to discrepancies between the theory and real-world devices. An eavesdropper can use these discrepancies to compromise the QKD security, thus legitimate sides need to estimate the influence of imperfections to prevent the loss of security. Here we investigate explicit eavesdropping attacks on passive side channels of the light source for a BB84 decoy states QKD protocol. We consider an optimal phase-covariant cloning attack, followed by unambiguous state discrimination and a joint measurement. Our calculations provide a hint that for state-of-the-art light sources the inherent presence of passive side channels still allows the protocol to be secure, albeit with the reduced secret key rates.
Though the BB84 protocol has provable security over a noiseless quantum channel, the security is not proven over current noisy technology. The level of tolerable error on such systems is still unclear, as is how much information about a raw key may be obtained by an eavesdropper. We develop a reproducible test to determine the security–or lack thereof–of the protocol in practice. This enables us to obtain an experimental estimate of the information that can be obtained using asymmetric phase-covariant cloning to eavesdrop on the BB84 protocol.
We present the results of a linear optics photonic implementation of a quantum circuit that simulates a phase covariant cloner. Input polarization qubit states are cloned into path qubit states of the same photon, which is identified as a potential eavesdropper in a quantum key distribution protocol. The device has the flexibility to simulate optimal and non-optimal cloning machines, as well as mirrored versions that optimally clone states on either the northern or southern hemispheres of the Bloch sphere. We experimentally simulate the effect of a single 1→21\rightarrow 21→2 cloner, as well as the action of a random sequence of the original cloner and its mirrored version. This procedure allows the eavesdropper to mitigate the amount of noise added to the original copy and therefore to mask its presence.