2,220 research outputs found
Unequal Error Protection Querying Policies for the Noisy 20 Questions Problem
In this paper, we propose an open-loop unequal-error-protection querying
policy based on superposition coding for the noisy 20 questions problem. In
this problem, a player wishes to successively refine an estimate of the value
of a continuous random variable by posing binary queries and receiving noisy
responses. When the queries are designed non-adaptively as a single block and
the noisy responses are modeled as the output of a binary symmetric channel the
20 questions problem can be mapped to an equivalent problem of channel coding
with unequal error protection (UEP). A new non-adaptive querying strategy based
on UEP superposition coding is introduced whose estimation error decreases with
an exponential rate of convergence that is significantly better than that of
the UEP repetition coding introduced by Variani et al. (2015). With the
proposed querying strategy, the rate of exponential decrease in the number of
queries matches the rate of a closed-loop adaptive scheme where queries are
sequentially designed with the benefit of feedback. Furthermore, the achievable
error exponent is significantly better than that of random block codes
employing equal error protection.Comment: To appear in IEEE Transactions on Information Theor
Enhancement of Secrecy of Block Ciphered Systems by Deliberate Noise
This paper considers the problem of end-end security enhancement by resorting
to deliberate noise injected in ciphertexts. The main goal is to generate a
degraded wiretap channel in application layer over which Wyner-type secrecy
encoding is invoked to deliver additional secure information. More
specifically, we study secrecy enhancement of DES block cipher working in
cipher feedback model (CFB) when adjustable and intentional noise is introduced
into encrypted data in application layer. A verification strategy in exhaustive
search step of linear attack is designed to allow Eve to mount a successful
attack in the noisy environment. Thus, a controllable wiretap channel is
created over multiple frames by taking advantage of errors in Eve's
cryptanalysis, whose secrecy capacity is found for the case of known channel
states at receivers. As a result, additional secure information can be
delivered by performing Wyner type secrecy encoding over super-frames ahead of
encryption, namely, our proposed secrecy encoding-then-encryption scheme. These
secrecy bits could be taken as symmetric keys for upcoming frames. Numerical
results indicate that a sufficiently large secrecy rate can be achieved by
selective noise addition.Comment: 11 pages, 8 figures, journa
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