9,441 research outputs found
Algorithms and Throughput Analysis for MDS-Coded Switches
Network switches and routers need to serve packet writes and reads at rates
that challenge the most advanced memory technologies. As a result, scaling the
switching rates is commonly done by parallelizing the packet I/Os using
multiple memory units. For improved read rates, packets can be coded with an
[n,k] MDS code, thus giving more flexibility at read time to achieve higher
utilization of the memory units. In the paper, we study the usage of [n,k] MDS
codes in a switching environment. In particular, we study the algorithmic
problem of maximizing the instantaneous read rate given a set of packet
requests and the current layout of the coded packets in memory. The most
interesting results from practical standpoint show how the complexity of
reaching optimal read rate depends strongly on the writing policy of the coded
packets.Comment: 6 pages, an extended version of a paper accepted to the 2015 IEEE
International Symposium on Information Theory (ISIT
PPP-Completeness with Connections to Cryptography
Polynomial Pigeonhole Principle (PPP) is an important subclass of TFNP with
profound connections to the complexity of the fundamental cryptographic
primitives: collision-resistant hash functions and one-way permutations. In
contrast to most of the other subclasses of TFNP, no complete problem is known
for PPP. Our work identifies the first PPP-complete problem without any circuit
or Turing Machine given explicitly in the input, and thus we answer a
longstanding open question from [Papadimitriou1994]. Specifically, we show that
constrained-SIS (cSIS), a generalized version of the well-known Short Integer
Solution problem (SIS) from lattice-based cryptography, is PPP-complete.
In order to give intuition behind our reduction for constrained-SIS, we
identify another PPP-complete problem with a circuit in the input but closely
related to lattice problems. We call this problem BLICHFELDT and it is the
computational problem associated with Blichfeldt's fundamental theorem in the
theory of lattices.
Building on the inherent connection of PPP with collision-resistant hash
functions, we use our completeness result to construct the first natural hash
function family that captures the hardness of all collision-resistant hash
functions in a worst-case sense, i.e. it is natural and universal in the
worst-case. The close resemblance of our hash function family with SIS, leads
us to the first candidate collision-resistant hash function that is both
natural and universal in an average-case sense.
Finally, our results enrich our understanding of the connections between PPP,
lattice problems and other concrete cryptographic assumptions, such as the
discrete logarithm problem over general groups
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