483 research outputs found
Active Internet Traffic Filtering: Real-time Response to Denial of Service Attacks
Denial of Service (DoS) attacks are one of the most challenging threats to
Internet security. An attacker typically compromises a large number of
vulnerable hosts and uses them to flood the victim's site with malicious
traffic, clogging its tail circuit and interfering with normal traffic. At
present, the network operator of a site under attack has no other resolution
but to respond manually by inserting filters in the appropriate edge routers to
drop attack traffic. However, as DoS attacks become increasingly sophisticated,
manual filter propagation becomes unacceptably slow or even infeasible.
In this paper, we present Active Internet Traffic Filtering, a new automatic
filter propagation protocol. We argue that this system provides a guaranteed,
significant level of protection against DoS attacks in exchange for a
reasonable, bounded amount of router resources. We also argue that the proposed
system cannot be abused by a malicious node to interfere with normal Internet
operation. Finally, we argue that it retains its efficiency in the face of
continued Internet growth.Comment: Briefly describes the core ideas of AITF, a protocol for facing
Denial of Service Attacks. 6 pages lon
Valence holes as Luttinger spinor based qubits in quantum dots
We present a theory of valence holes as Luttinger spinor based qubits in
p-doped self-assembled quantum dots within the 4-band formalism. The
two qubit levels are identified with the two chiralities of the doubly
degenerate ground state. We show that single qubit operations can be
implemented with static magnetic field applied along the and
directions, acting analogously to the and
operators in the qubit subspace respectively. The coupling of two dots and
hence the double qubit operations are shown to be sensitive to the orientation
of the two quantum dots. For vertical qubit arrays, there exists an optimal
qubit separation suitable for the voltage control of qubit-qubit interactions
On the complexity of inverting integer and polynomial matrices
Abstract An algorithm is presented that probabilistically computes the exact inverse of a nonsingular n Ă n integer matrix A using OË(n 3 (log ||A|| + log Îș(A))) bit operations. Here, ||A|| = max ij |A ij | denotes the largest entry in absolute value, Îș(A) := ||A â1 || ||A|| is the condition number of the input matrix, and the soft-O notation OËindicates some missing log n and log log ||A|| factors. A variation of the algorithm is presented for polynomial matrices. The inverse of any nonsingular n Ă n matrix whose entries are polynomials of degree d over a field can be computed using an expected number of OË(n 3 d) field operations. Both algorithms are randomized of the Las Vegas type: fail may be returned with probability at most 1/2, and if fail is not returned the output is certified to be correct in the same running time bound
Sea-level rise will drive divergent sediment transport patterns on fore reefs and reef flats, potentially causing erosion on Atoll Islands
Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Earth Surface 125 (2020): e2019JF005446, doi: 10.1029/2019JF005446.Atoll reef islands primarily consist of unconsolidated sediment, and their oceanâfacing shorelines are maintained by sediment produced and transported across their reefs. Changes in incident waves can alter crossâshore sediment exchange and, thus, affect the sediment budget and morphology of atoll reef islands. Here we investigate the influence of sea level rise and projected wave climate change on wave characteristics and crossâshore sediment transport across an atoll reef at Kwajalein Island, Republic of the Marshall Islands. Using a phaseâresolving model, we quantify the influence on sediment transport of quantities not well captured by waveâaveraged models, namely, wave asymmetry and skewness and flow acceleration. Model results suggest that for current reef geometry, sea level, and wave climate, potential bedload transport is directed onshore, decreases from the fore reef to the beach, and is sensitive to the influence of flow acceleration. We find that a projected 12% decrease in annual wave energy by 2100 CE has negligible influence on reef flat hydrodynamics. However, 0.5â2.0 m of sea level rise increases wave heights, skewness, and shear stress on the reef flat and decreases wave skewness and shear stress on the fore reef. These hydrodynamic changes decrease potential sediment inputs onshore from the fore reef where coral production is greatest but increase potential crossâreef sediment transport from the outer reef flat to the beach. Assuming sediment production on the fore reef remains constant or decreases due to increasing ocean temperatures and acidification, these processes have the potential to decrease net sediment delivery to atoll islands, causing erosion.This study was supported by the Strategic Environmental Research and Development Program through awards SERDP: RCâ2334, and RCâ2336. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.2021-03-2
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