Full-field implementation of a perfect eavesdropper on a quantum cryptography system

Abstract

Quantum key distribution (QKD) allows two remote parties to grow a shared secret key. Its security is founded on the principles of quantum mechanics, but in reality it significantly relies on the physical implementation. Technological imperfections of QKD systems have been previously explored, but no attack on an established QKD connection has been realized so far. Here we show the first full-field implementation of a complete attack on a running QKD connection. An installed eavesdropper obtains the entire 'secret' key, while none of the parameters monitored by the legitimate parties indicate a security breach. This confirms that non-idealities in physical implementations of QKD can be fully practically exploitable, and must be given increased scrutiny if quantum cryptography is to become highly secure.

Finite-key analysis for measurement-device-independent quantum key distribution

“…Its feasibility has been promptly demonstrated both in laboratories and via field tests [24][25][26][27] . It successfully removes all (existing and yet to be discovered) detector side channels 3,5,6,[9][10][11] , which, arguably, is the most critical part of most QKD implementations. Importantly, in contrast to diQKD, this solution does not require that Alice and Bob perform a loophole-free Bell test; it is enough if they prove the presence of entanglement in a quantum state that is effectively distributed between them, just like in standard QKD schemes 28 .…”

“…In practice, however, it does not, as most practical devices behave differently from the theoretical models assumed in the security proofs. As a result, we face implementation loopholes, or so-called side channels, which may be used by adversaries without being detected, as seen in recent attacks against certain commercial QKD systems [3][4][5][6][7][8][9][10][11] .…”

New Quantum Cipher Optical Communication: Y-00

“…These conditions become a loop hole. Therefore that disables absolutely secure key distribution and deteriorates safety level to allow eavesdropping [7,8]. For this reason, the practical use of the QKD system is difficult while maintaining safety in the current optical communication system.…”

Using quantum key distribution for cryptographic purposes: A survey

“…This "double trust assumption" is directly challenged by the demonstration of successful attacks [49,50] on QKD implementations, as it will be discussed in 5.1. As a consequence, backing up this trust assumption on QKD implementation will imply to develop and implement counter-measures to known attacks and certification procedures for QKD devices in the same spirit as what exists today for (classical) cryptographic hardware.…”

“…Many of the published attacks have been realized by exploiting existing or induced imperfections of APDs. In the detector blinding attack [102,49], an intense pulse of light is used to change the detector response characteristics, allowing then to use faked-states sent by Eve to mimic a correct behavior [103,104] (with respect to the observation of correct detection statistics as well as correct correlations between Alice and Bob's measurements) while breaking the security of the QKD protocol since the detector response is manipulated by Eve. Many implementations rely on several APDs (for example one per detection basis in BB84) and a lack of symmetry between the detectors can be exploited to launch attacks.…”