89,621 research outputs found
A Semantic Hierarchy for Erasure Policies
We consider the problem of logical data erasure, contrasting with physical
erasure in the same way that end-to-end information flow control contrasts with
access control. We present a semantic hierarchy for erasure policies, using a
possibilistic knowledge-based semantics to define policy satisfaction such that
there is an intuitively clear upper bound on what information an erasure policy
permits to be retained. Our hierarchy allows a rich class of erasure policies
to be expressed, taking account of the power of the attacker, how much
information may be retained, and under what conditions it may be retained.
While our main aim is to specify erasure policies, the semantic framework
allows quite general information-flow policies to be formulated for a variety
of semantic notions of secrecy.Comment: 18 pages, ICISS 201
Erasure Coding for Real-Time Streaming
We consider a real-time streaming system where messages are created
sequentially at the source, and are encoded for transmission to the receiver
over a packet erasure link. Each message must subsequently be decoded at the
receiver within a given delay from its creation time. The goal is to construct
an erasure correction code that achieves the maximum message size when all
messages must be decoded by their respective deadlines under a specified set of
erasure patterns (erasure model). We present an explicit intrasession code
construction that is asymptotically optimal under erasure models containing a
limited number of erasures per coding window, per sliding window, and
containing erasure bursts of a limited length.Comment: Extended version of a conference paper in the IEEE International
Symposium on Information Theory (ISIT), July 2012. 12 pages, 3 figure
Comments on Information Erasure in Black Hole
We analyze the Kim, Lee & Lee model of information erasure by black holes and
find contradictions with standard physical laws. We demonstrate that the
erasure model leads to arbitrarily fast information erasure; the proposed
physical interpretation of information freezing at the event horizon as
observed by an asymptotic observer is problematic; and information erasure,
whatever the process may be, near the black hole horizon leads to
contradictions with quantum mechanics if Landauer's principle is assumed. The
later part of the work demonstrates the significance of the "erasure entropy."
We show that the erasure entropy is the mutual information between two
subsystems.Comment: 13 pages, clarified some issues in detai
Faulty Successive Cancellation Decoding of Polar Codes for the Binary Erasure Channel
We study faulty successive cancellation decoding of polar codes for the
binary erasure channel. To this end, we introduce a simple erasure-based fault
model and we show that, under this model, polarization does not happen, meaning
that fully reliable communication is not possible at any rate. Moreover, we
provide numerical results for the frame erasure rate and bit erasure rate and
we study an unequal error protection scheme that can significantly improve the
performance of the faulty successive cancellation decoder with negligible
overhead.Comment: As presented at ISITA 201
Dependency-aware unequal erasure protection codes
Classical unequal erasure protection schemes split data to be protected into classes which are encoded independently. The unequal protection scheme presented in this paper is based on an erasure code which encodes all the data together according to the existing dependencies. A simple algorithm generates dynamically the generator matrix of the erasure code according to the packets streams structure, i.e., the dependencies between the packets, and the rate of the code. This proposed erasure code was applied to a packetized MPEG4 stream transmitted over a packet erasure channel and compared with other classical protection schemes in terms of PSNR and MOS. It is shown that the proposed code allows keeping a high video quality-level in a larger packet loss rate range than the other protection schemes
Systematic MDS erasure codes based on vandermonde matrices
An increasing number of applications in computer communications uses erasure codes to cope with packet losses. Systematic maximum-distance separable (MDS) codes are often the best adapted codes. This letter introduces new systematic MDS erasure codes constructed from two Vandermonde matrices. These codes have lower coding and decoding complexities than the others systematic MDS erasure codes
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