TY - JOUR
T1 - Continuous-variable quantum cryptography with an untrusted relay
T2 - detailed security analysis of the symmetric configuration
AU - Ottaviani, Carlo
AU - Spedalieri, Gae
AU - Braunstein, Samuel Leon
AU - Pirandola, Stefano
PY - 2015/2/18
Y1 - 2015/2/18
N2 - We consider the continuous-variable protocol of Pirandola et al. [Nature Photonics 9, 397-402 (2015), see also arXiv.1312.4104] where the secret key is established by the measurement of an untrusted relay. In this network protocol, two authorized parties are connected to an untrusted relay by insecure quantum links. Secret correlations are generated by a continuous-variable Bell detection performed on incoming coherent states. In the present work we provide a detailed study of the symmetric configuration, where the relay is midway between the parties. We analyze symmetric eavesdropping strategies against the quantum links explicitly showing that, at fixed transmissivity and thermal noise, two-mode coherent attacks are optimal, manifestly outperforming one-mode collective attacks based on independent entangling cloners. Such an advantage is shown both in terms of security threshold and secret-key rate.
AB - We consider the continuous-variable protocol of Pirandola et al. [Nature Photonics 9, 397-402 (2015), see also arXiv.1312.4104] where the secret key is established by the measurement of an untrusted relay. In this network protocol, two authorized parties are connected to an untrusted relay by insecure quantum links. Secret correlations are generated by a continuous-variable Bell detection performed on incoming coherent states. In the present work we provide a detailed study of the symmetric configuration, where the relay is midway between the parties. We analyze symmetric eavesdropping strategies against the quantum links explicitly showing that, at fixed transmissivity and thermal noise, two-mode coherent attacks are optimal, manifestly outperforming one-mode collective attacks based on independent entangling cloners. Such an advantage is shown both in terms of security threshold and secret-key rate.
KW - quant-ph
KW - physics.optics
U2 - 10.1103/PhysRevA.91.022320
DO - 10.1103/PhysRevA.91.022320
M3 - Article
SN - 1050-2947
VL - 91
JO - Physical Review A (Atomic, Molecular and Optical Physics)
JF - Physical Review A (Atomic, Molecular and Optical Physics)
IS - 2
M1 - 022320
ER -