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arXiv:1402.2250 · Physical Review A

Counterfactual quantum certificate authorization

Akshata Shenoy H., R. Srikanth, T. Srinivas

Published May 8, 2014• 19 citations
arXivHTMLPDF

Abstract

We present a multipartite protocol in a counterfactual paradigm. In counterfactual quantum cryptography, secure information is transmitted between two spatially separated parties even when there is no physical travel of particles transferring the information between them. We propose here a tripartite counterfactual quantum protocol for the task of certificate authorization. Here a trusted third party, Alice, authenticates an entity Bob (e.g., a bank) that a client Charlie wishes to securely transact with. The protocol is counterfactual with respect to either Bob or Charlie. We prove its security against a general incoherent attack, where Eve attacks single particles.

DOI
10.1103/physreva.89.052307

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We present a multipartite protocol in a counterfactual paradigm. In counterfactual quantum cryptography, secure information is transmitted between two spatially separated parties even when there is no physical travel of particles transferring the information between them. We propose here a tripartite counterfactual quantum protocol for the task of certificate authorization. Here a trusted third party, Alice, authenticates an entity Bob (e.g., a bank) that a client Charlie wishes to securely transact with. The protocol is counterfactual with respect to either Bob or Charlie. We prove its security against a general incoherent attack, where Eve attacks single particles.
Counterfactual communication refers to cases in which information is exchanged between two remote parties without actual transmission of physical particles. We propose a fully tripartite counterfactual quantum protocol for the task of identity authentication. Here, a trusted certificate authority (Charlie) enables a client (Alice) and an entity (Bob) to share a secure random key based on the modification of early protocols by Aharonov and Vaidman, therefore permitting communication that is counterfactual according to the two-state vector formalism. The protocol has high robustness against environmental noise, while still passing the Fisher information test. With semi-honest Charlie, the counterfactual protocol transforms identity authorization into quantum-assisted key distribution. We show that the counterfactual quantum key distribution can be made secure within a twin-field framework. Our simulation results show that the maximal secure distance of the counterfactual protocol with a practical weak coherent state is around 190 km.
In counterfactual quantum key distribution (QKD), two remote parties can securely share random polarization-encoded bits through the blocking rather than the transmission of particles. We propose a semi-counterfactual QKD, i.e. , one where the secret bit is shared, and also encoded, based on the blocking or non-blocking of a particle. The scheme is thus semi-counterfactual and not based on polarization encoding. As with other counterfactual schemes and the Goldenberg-Vaidman protocol, but unlike BB84, the encoding states are orthogonal and security arises ultimately from single-particle non-locality. Unlike any of them, however, the secret bit generated is maximally indeterminate until the joint action of Alice and Bob. We prove the general security of the protocol, and study the most general photon-number–preserving incoherent attack in detail.
In counterfactual quantum key distribution (QKD), two remote parties can share a secure \nsecret random key even without transmission of a physical particle (a non-vacuum pulse) through the \nchannel. A QKD scheme is proposed which is counterfactual in one of the bits, and in which the secret bits \nare not encoded in the polarization, but in the joint action of Alice and Bob. On the conceptual level, our \nscheme throws new light on the origin of security in counterfactual cryptography. On the practical side, \nnon-polarization encoding makes it robust against certain trojan horse attacks. We study the the general \nphoton-number preserving incoherent attack in detail.