# Upper bounds for the security of two distributed-phase reference protocols of quantum cryptography

 Authors: C Branciard, N Gisin, V Scarani New Journal of Physics 10, 013031 (2008) http://dx.doi.org/10.1088/1367-2630/10/1/013031 The differential-phase-shift (DPS) and the coherent-one-way (COW) are among the most practical protocols for quantum cryptography, and are therefore the object of fast-paced experimental developments. The assessment of their security is also a challenge for theorists: the existing tools, that allow to prove security against the most general attacks, do not apply to these two protocols in any straightforward way. We present new upper bounds for their security in the limit of large distances (d greater than or similar to 50 km with typical values in optical fibers) by considering a large class of collective attacks, namely those in which the adversary attaches ancillary quantum systems to each pulse or to each pair of pulses. We introduce also two modified versions of the COW protocol, which may prove more robust than the original one. njp8_1_013031_cowvsdps.pdf

# BibTeX Source

@Article{Branciard2008,
author =       "C. Branciard and N. Gisin and V. Scarani",
title =        "Upper bounds for the security of two distributed-phase reference protocols of
quantum cryptography",
journal =      "New Journal of Physics",
year =         "2008",
volume =       "10",
pages =        "013031",
abstract =     "The differential-phase-shift (DPS) and the coherent-one-way (COW) are among the
most practical protocols for quantum cryptography, and are therefore the object of
fast-paced experimental developments. The assessment of their security is also a
challenge for theorists: the existing tools, that allow to prove security against
the most general attacks, do not apply to these two protocols in any
straightforward way. We present new upper bounds for their security in the limit of
large distances (d greater than or similar to 50 km with typical values in optical
fibers) by considering a large class of collective attacks, namely those in which
the adversary attaches ancillary quantum systems to each pulse or to each pair of
pulses. We introduce also two modified versions of the COW protocol, which may
prove more robust than the original one.",
doi =          "10.1088/1367-2630/10/1/013031",
owner =        "cc",
sn =           "1367-2630",
timestamp =    "2010.08.20",
ut =           "WOS:000253085100003",
}