15,460 research outputs found
Learning Character Strings via Mastermind Queries, with a Case Study Involving mtDNA
We study the degree to which a character string, , leaks details about
itself any time it engages in comparison protocols with a strings provided by a
querier, Bob, even if those protocols are cryptographically guaranteed to
produce no additional information other than the scores that assess the degree
to which matches strings offered by Bob. We show that such scenarios allow
Bob to play variants of the game of Mastermind with so as to learn the
complete identity of . We show that there are a number of efficient
implementations for Bob to employ in these Mastermind attacks, depending on
knowledge he has about the structure of , which show how quickly he can
determine . Indeed, we show that Bob can discover using a number of
rounds of test comparisons that is much smaller than the length of , under
reasonable assumptions regarding the types of scores that are returned by the
cryptographic protocols and whether he can use knowledge about the distribution
that comes from. We also provide the results of a case study we performed
on a database of mitochondrial DNA, showing the vulnerability of existing
real-world DNA data to the Mastermind attack.Comment: Full version of related paper appearing in IEEE Symposium on Security
and Privacy 2009, "The Mastermind Attack on Genomic Data." This version
corrects the proofs of what are now Theorems 2 and 4
OpenACC Based GPU Parallelization of Plane Sweep Algorithm for Geometric Intersection
Line segment intersection is one of the elementary operations in computational geometry. Complex problems in Geographic Information Systems (GIS) like finding map overlays or spatial joins using polygonal data require solving segment intersections. Plane sweep paradigm is used for finding geometric intersection in an efficient manner. However, it is difficult to parallelize due to its in-order processing of spatial events. We present a new fine-grained parallel algorithm for geometric intersection and its CPU and GPU implementation using OpenMP and OpenACC. To the best of our knowledge, this is the first work demonstrating an effective parallelization of plane sweep on GPUs.
We chose compiler directive based approach for implementation because of its simplicity to parallelize sequential code. Using Nvidia Tesla P100 GPU, our implementation achieves around 40X speedup for line segment intersection problem on 40K and 80K data sets compared to sequential CGAL library
Spin-the-bottle Sort and Annealing Sort: Oblivious Sorting via Round-robin Random Comparisons
We study sorting algorithms based on randomized round-robin comparisons.
Specifically, we study Spin-the-bottle sort, where comparisons are
unrestricted, and Annealing sort, where comparisons are restricted to a
distance bounded by a \emph{temperature} parameter. Both algorithms are simple,
randomized, data-oblivious sorting algorithms, which are useful in
privacy-preserving computations, but, as we show, Annealing sort is much more
efficient. We show that there is an input permutation that causes
Spin-the-bottle sort to require expected time in order to
succeed, and that in time this algorithm succeeds with high
probability for any input. We also show there is an implementation of Annealing
sort that runs in time and succeeds with very high probability.Comment: Full version of a paper appearing in ANALCO 2011, in conjunction with
SODA 201
Poets in dialogue, dialogues in poets
Is there something noticeably peculiar about dialogues with poets when transformed into writing, be it in electronic or printed form? The pauses and hesitations, the thrust and parry, the slurrings and overlappings of ordinary speech by and large disappear. In their place is an artifice, a deliberate creation of a script, with questions and responses clearly marked for our attention. Might we be approaching a tidied duologue which, some might also cynically remark, largely reproduces a dual monologue? Moreover, when poets are in dialogue, with whom or what does the poet converse
- …