462 research outputs found
Quantum Key Distribution Using Quantum Faraday Rotators
We propose a new quantum key distribution (QKD) protocol based on the fully
quantum mechanical states of the Faraday rotators. The protocol is
unconditionally secure against collective attacks for multi-photon source up to
two photons on a noisy environment. It is also robust against impersonation
attacks. The protocol may be implemented experimentally with the current
spintronics technology on semiconductors.Comment: 7 pages, 7 EPS figure
Stronger Attacks on Causality-Based Key Agreement
Remarkably, it has been shown that in principle, security proofs for quantum
key-distribution (QKD) protocols can be independent of assumptions on the
devices used and even of the fact that the adversary is limited by quantum
theory. All that is required instead is the absence of any hidden information
flow between the laboratories, a condition that can be enforced either by
shielding or by space-time causality. All known schemes for such Causal Key
Distribution (CKD) that offer noise-tolerance (and, hence, must use privacy
amplification as a crucial step) require multiple devices carrying out
measurements in parallel on each end of the protocol, where the number of
devices grows with the desired level of security. We investigate the power of
the adversary for more practical schemes, where both parties each use a single
device carrying out measurements consecutively. We provide a novel construction
of attacks that is strictly more powerful than the best known attacks and has
the potential to decide the question whether such practical CKD schemes are
possible in the negative
Security bounds for continuous variables quantum key distribution
Security bounds for key distribution protocols using coherent and squeezed
states and homodyne measurements are presented. These bounds refer to (i)
general attacks and (ii) collective attacks where Eve interacts individually
with the sent states, but delays her measurement until the end of the
reconciliation process. For the case of a lossy line and coherent states, it is
first proven that a secure key distribution is possible up to 1.9 dB of losses.
For the second scenario, the security bounds are the same as for the completely
incoherent attack.Comment: See also F. Grosshans, quant-ph/040714
- …