27 research outputs found
Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law-Johnson-noise secure key exchange
We classify and analyze bit errors in the current measurement mode of the
Kirchhoff-law-Johnson-noise (KLJN) key distribution. The error probability
decays exponentially with increasing bit exchange period and fixed bandwidth,
which is similar to the error probability decay in the voltage measurement
mode. We also analyze the combination of voltage and current modes for error
removal. In this combination method, the error probability is still an
exponential function that decays with the duration of the bit exchange period,
but it has superior fidelity to the former schemes.Comment: 9 pages, accepted for publication in Journal of Computational
Electronic
Long Response to Scheuer-Yariv: "A Classical Key-Distribution System based on Johnson (like) noise - How Secure?", physics/0601022
This is the longer (partially unpublished) version of response; the shorter
version (http://arxiv.org/abs/physics/0605013) is published in Physics Letters
A. We point out that the claims in the comment-paper of Scheuer and Yariv are
either irrelevant or incorrect. We first clarify what the security of a
physically secure layer means. The idealized Kirchoff-loop-Johnson-like-noise
(KLJN) scheme is totally secure therefore it is more secure than idealized
quantum communication schemes which can never be totally secure because of the
inherent noise processes in those communication schemes and the statistical
nature of eavesdropper detection based on error statistics. On the other hand,
with sufficient resources, a practical/non-ideal realization of the KLJN cipher
can arbitrarily approach the idealized limit and outperform even the idealized
quantum communicator schemes because the non-ideality-effects are determined
and controlled by the design. The cable resistance issue analyzed by Scheuer
and Yariv is a good example for that because the eavesdropper has insufficient
time window to build a sufficient statistics and the actual information leak
can be designed. We show that Scheuer's and Yariv's numerical result of 1%
voltage drop supports higher security than that of quantum communicators.
Moreover, choosing thicker or shorter wires can arbitrarily reduce this voltage
drop further; the same conclusion holds even according to the equations of
Scheuer and Yariv.Comment: The older long response and the newer brief response (in press, PLA)
with modelling data are fuse
Critical analysis of the Bennett-Riedel attack on secure cryptographic key distributions via the Kirchhoff-law-Johnson-noise scheme
Recently, Bennett and Riedel (BR) (http://arxiv.org/abs/1303.7435v1) argued that thermodynamics is not essential in the Kirchhoff-law鈥揓ohnson-noise (KLJN) classical physical cryptographic exchange method in an effort to disprove the security of the KLJN scheme. They attempted to demonstrate this by introducing a dissipation-free deterministic key exchange method with two batteries and two switches. In the present paper, we first show that BR's scheme is unphysical and that some elements of its assumptions violate basic protocols of secure communication. All our analyses are based on a technically unlimited Eve with infinitely accurate and fast measurements limited only by the laws of physics and statistics. For non-ideal situations and at active (invasive) attacks, the uncertainly principle between measurement duration and statistical errors makes it impossible for Eve to extract the key regardless of the accuracy or speed of her measurements. To show that thermodynamics and noise are essential for the security, we crack the BR system with 100% success via passive attacks, in ten different ways, and demonstrate that the same cracking methods do not function for the KLJN scheme that employs Johnson noise to provide security underpinned by the Second Law of Thermodynamics. We also present a critical analysis of some other claims by BR; for example, we prove that their equations for describing zero security do not apply to the KLJN scheme. Finally we give mathematical security proofs for each BR-attack against the KLJN scheme and conclude that the information theoretic (unconditional) security of the KLJN method has not been successfully challenged.Laszlo B. Kish, Derek Abbott, Claes G. Granqvis
Current Injection Attack against the KLJN Secure Key Exchange
The Kirchhoff-law-Johnson-noise (KLJN) scheme is a statistical/physical
secure key exchange system based on the laws of classical statistical physics
to provide unconditional security. We used the LTSPICE industrial cable and
circuit simulator to emulate one of the major active (invasive) attacks, the
current injection attack, against the ideal and a practical KLJN system,
respectively. We show that two security enhancement techniques, namely, the
instantaneous voltage/current comparison method, and a simple privacy
amplification scheme, independently and effectively eliminate the information
leak and successfully preserve the system's unconditional security
On the "cracking" scheme in the paper "A directional coupler attack against the Kish key distribution system" by Gunn, Allison and Abbott
Recently, Gunn, Allison and Abbott (GAA)
[http://arxiv.org/pdf/1402.2709v2.pdf] proposed a new scheme to utilize
electromagnetic waves for eavesdropping on the Kirchhoff-law-Johnson-noise
(KLJN) secure key distribution. We proved in a former paper [Fluct. Noise Lett.
13 (2014) 1450016] that GAA's mathematical model is unphysical. Here we analyze
GAA's cracking scheme and show that, in the case of a loss-free cable, it
provides less eavesdropping information than in the earlier
(Bergou)-Scheuer-Yariv mean-square-based attack [Kish LB, Scheuer J, Phys.
Lett. A 374 (2010) 2140-2142], while it offers no information in the case of a
lossy cable. We also investigate GAA's claim to be experimentally capable of
distinguishing - using statistics over a few correlation times only - the
distributions of two Gaussian noises with a relative variance difference of
less than 10^-8. Normally such distinctions would require hundreds of millions
of correlations times to be observable. We identify several potential
experimental artifacts as results of poor KLJN design, which can lead to GAA's
assertions: deterministic currents due to spurious harmonic components caused
by ground loops, DC offset, aliasing, non-Gaussian features including
non-linearities and other non-idealities in generators, and the time-derivative
nature of GAA's scheme which tends to enhance all of these artifacts.Comment: This version is accepted for publication in Metrology and Measurement
System
Cable Capacitance Attack against the KLJN Secure Key Exchange
The security of the Kirchhoff-law-Johnson-(like)-noise (KLJN) key exchange
system is based on the Fluctuation-Dissipation-Theorem of classical statistical
physics. Similarly to quantum key distribution, in practical situations, due to
the non-idealities of the building elements, there is a small information leak,
which can be mitigated by privacy amplification or other techniques so that the
unconditional (information theoretic) security is preserved. In this paper, the
industrial cable and circuit simulator LTSPICE is used to validate the
information leak due to one of the non-idealities in KLJN, the parasitic
(cable) capacitance. Simulation results show that privacy amplification and/or
capacitor killer (capacitance compensation) arrangements can effectively
eliminate the leak.Comment: Accepted for publication in the journal: Informatio