1,268 research outputs found
The Private Key Capacity of a Cooperative Pairwise-Independent Network
This paper studies the private key generation of a cooperative
pairwise-independent network (PIN) with M+2 terminals (Alice, Bob and M
relays), M >= 2. In this PIN, the correlated sources observed by every pair of
terminals are independent of those sources observed by any other pair of
terminal. All the terminals can communicate with each other over a public
channel which is also observed by Eve noiselessly. The objective is to generate
a private key between Alice and Bob under the help of the M relays; such a
private key needs to be protected not only from Eve but also from individual
relays simultaneously. The private key capacity of this PIN model is
established, whose lower bound is obtained by proposing a novel random binning
(RB) based key generation algorithm, and the upper bound is obtained based on
the construction of M enhanced source models. The two bounds are shown to be
exactly the same. Then, we consider a cooperative wireless network and use the
estimates of fading channels to generate private keys. It has been shown that
the proposed RB-based algorithm can achieve a multiplexing gain M-1, an
improvement in comparison with the existing XOR- based algorithm whose
achievable multiplexing gain is about [M]/2.Comment: 5 pages, 3 figures, IEEE ISIT 2015 (to appear
Compressed Secret Key Agreement: Maximizing Multivariate Mutual Information Per Bit
The multiterminal secret key agreement problem by public discussion is
formulated with an additional source compression step where, prior to the
public discussion phase, users independently compress their private sources to
filter out strongly correlated components for generating a common secret key.
The objective is to maximize the achievable key rate as a function of the joint
entropy of the compressed sources. Since the maximum achievable key rate
captures the total amount of information mutual to the compressed sources, an
optimal compression scheme essentially maximizes the multivariate mutual
information per bit of randomness of the private sources, and can therefore be
viewed more generally as a dimension reduction technique. Single-letter lower
and upper bounds on the maximum achievable key rate are derived for the general
source model, and an explicit polynomial-time computable formula is obtained
for the pairwise independent network model. In particular, the converse results
and the upper bounds are obtained from those of the related secret key
agreement problem with rate-limited discussion. A precise duality is shown for
the two-user case with one-way discussion, and such duality is extended to
obtain the desired converse results in the multi-user case. In addition to
posing new challenges in information processing and dimension reduction, the
compressed secret key agreement problem helps shed new light on resolving the
difficult problem of secret key agreement with rate-limited discussion, by
offering a more structured achieving scheme and some simpler conjectures to
prove
The Sender-Excited Secret Key Agreement Model: Capacity, Reliability and Secrecy Exponents
We consider the secret key generation problem when sources are randomly
excited by the sender and there is a noiseless public discussion channel. Our
setting is thus similar to recent works on channels with action-dependent
states where the channel state may be influenced by some of the parties
involved. We derive single-letter expressions for the secret key capacity
through a type of source emulation analysis. We also derive lower bounds on the
achievable reliability and secrecy exponents, i.e., the exponential rates of
decay of the probability of decoding error and of the information leakage.
These exponents allow us to determine a set of strongly-achievable secret key
rates. For degraded eavesdroppers the maximum strongly-achievable rate equals
the secret key capacity; our exponents can also be specialized to previously
known results.
In deriving our strong achievability results we introduce a coding scheme
that combines wiretap coding (to excite the channel) and key extraction (to
distill keys from residual randomness). The secret key capacity is naturally
seen to be a combination of both source- and channel-type randomness. Through
examples we illustrate a fundamental interplay between the portion of the
secret key rate due to each type of randomness. We also illustrate inherent
tradeoffs between the achievable reliability and secrecy exponents. Our new
scheme also naturally accommodates rate limits on the public discussion. We
show that under rate constraints we are able to achieve larger rates than those
that can be attained through a pure source emulation strategy.Comment: 18 pages, 8 figures; Submitted to the IEEE Transactions on
Information Theory; Revised in Oct 201
Communication Complexity of the Secret Key Agreement in Algorithmic Information Theory
It is known that the mutual information, in the sense of Kolmogorov
complexity, of any pair of strings x and y is equal to the length of the
longest shared secret key that two parties can establish via a probabilistic
protocol with interaction on a public channel, assuming that the parties hold
as their inputs x and y respectively. We determine the worst-case communication
complexity of this problem for the setting where the parties can use private
sources of random bits. We show that for some x, y the communication complexity
of the secret key agreement does not decrease even if the parties have to agree
on a secret key whose size is much smaller than the mutual information between
x and y. On the other hand, we discuss examples of x, y such that the
communication complexity of the protocol declines gradually with the size of
the derived secret key. The proof of the main result uses spectral properties
of appropriate graphs and the expander mixing lemma, as well as information
theoretic techniques.Comment: 33 pages, 6 figures. v3: the full version of the MFCS 2020 pape
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