374 research outputs found
Guessing a password over a wireless channel (on the effect of noise non-uniformity)
A string is sent over a noisy channel that erases some of its characters.
Knowing the statistical properties of the string's source and which characters
were erased, a listener that is equipped with an ability to test the veracity
of a string, one string at a time, wishes to fill in the missing pieces. Here
we characterize the influence of the stochastic properties of both the string's
source and the noise on the channel on the distribution of the number of
attempts required to identify the string, its guesswork. In particular, we
establish that the average noise on the channel is not a determining factor for
the average guesswork and illustrate simple settings where one recipient with,
on average, a better channel than another recipient, has higher average
guesswork. These results stand in contrast to those for the capacity of wiretap
channels and suggest the use of techniques such as friendly jamming with
pseudo-random sequences to exploit this guesswork behavior.Comment: Asilomar Conference on Signals, Systems & Computers, 201
Side-Information Coding with Turbo Codes and its Application to Quantum Key Distribution
Turbo coding is a powerful class of forward error correcting codes, which can
achieve performances close to the Shannon limit. The turbo principle can be
applied to the problem of side-information source coding, and we investigate
here its application to the reconciliation problem occurring in a
continuous-variable quantum key distribution protocol.Comment: 3 pages, submitted to ISITA 200
Strong Converse for a Degraded Wiretap Channel via Active Hypothesis Testing
We establish an upper bound on the rate of codes for a wiretap channel with
public feedback for a fixed probability of error and secrecy parameter. As a
corollary, we obtain a strong converse for the capacity of a degraded wiretap
channel with public feedback. Our converse proof is based on a reduction of
active hypothesis testing for discriminating between two channels to coding for
wiretap channel with feedback.Comment: This paper was presented at Allerton 201
Expurgation Exponent of Leaked Information in Privacy Amplification for Binary Sources
We investigate the privacy amplification problem in which Eve can observe the
uniform binary source through a binary erasure channel (BEC) or a binary
symmetric channel (BSC). For this problem, we derive the so-called expurgation
exponent of the information leaked to Eve. The exponent is derived by relating
the leaked information to the error probability of the linear code that is
generated by the linear hash function used in the privacy amplification, which
is also interesting in its own right. The derived exponent is larger than
state-of-the-art exponent recently derived by Hayashi at low rate.Comment: 5 pages, 7 figures, to be presented at IEEE Information Theory
Workshop (ITW) 201
Rate Compatible Protocol for Information Reconciliation: An application to QKD
Information Reconciliation is a mechanism that allows to weed out the
discrepancies between two correlated variables. It is an essential component in
every key agreement protocol where the key has to be transmitted through a
noisy channel. The typical case is in the satellite scenario described by
Maurer in the early 90's. Recently the need has arisen in relation with Quantum
Key Distribution (QKD) protocols, where it is very important not to reveal
unnecessary information in order to maximize the shared key length. In this
paper we present an information reconciliation protocol based on a rate
compatible construction of Low Density Parity Check codes. Our protocol
improves the efficiency of the reconciliation for the whole range of error
rates in the discrete variable QKD context. Its adaptability together with its
low interactivity makes it specially well suited for QKD reconciliation
Secret-key generation from wireless channels: Mind the reflections
Secret-key generation in a wireless environment exploiting the randomness and
reciprocity of the channel gains is considered. A new channel model is proposed
which takes into account the effect of reflections (or re-radiations) from
receive antenna elements, thus capturing an physical property of practical
antennas. It turns out that the reflections have a deteriorating effect on the
achievable secret-key rate between the legitimate nodes at high
signal-to-noise-power-ratio (SNR). The insights provide guidelines in the
design and operation of communication systems using the properties of the
wireless channel to prevent eavesdropping.Comment: 6 pages, 9 figure
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