162 research outputs found
Breakdown of the Landauer bound for information erasure in the quantum regime
A known aspect of the Clausius inequality is that an equilibrium system
subjected to a squeezing \d S of its entropy must release at least an amount
|\dbarrm Q|=T|\d S| of heat. This serves as a basis for the Landauer
principle, which puts a lower bound for the heat generated by erasure
of one bit of information. Here we show that in the world of quantum
entanglement this law is broken. A quantum Brownian particle interacting with
its thermal bath can either generate less heat or even {\it adsorb} heat during
an analogous squeezing process, due to entanglement with the bath. The effect
exists even for weak but fixed coupling with the bath, provided that
temperature is low enough. This invalidates the Landauer bound in the quantum
regime, and suggests that quantum carriers of information can be much more
efficient than assumed so far.Comment: 13 pages, revtex, 2 eps figure
Distributed Management of Massive Data: an Efficient Fine-Grain Data Access Scheme
This paper addresses the problem of efficiently storing and accessing massive
data blocks in a large-scale distributed environment, while providing efficient
fine-grain access to data subsets. This issue is crucial in the context of
applications in the field of databases, data mining and multimedia. We propose
a data sharing service based on distributed, RAM-based storage of data, while
leveraging a DHT-based, natively parallel metadata management scheme. As
opposed to the most commonly used grid storage infrastructures that provide
mechanisms for explicit data localization and transfer, we provide a
transparent access model, where data are accessed through global identifiers.
Our proposal has been validated through a prototype implementation whose
preliminary evaluation provides promising results
Provably Secure Double-Block-Length Hash Functions in a Black-Box Model
In CRYPTO’89, Merkle presented three double-block-length
hash functions based on DES. They are optimally collision resistant in
a black-box model, that is, the time complexity of any collision-finding
algorithm for them is Ω(2^<l/2>) if DES is a random block cipher, where
l is the output length. Their drawback is that their rates are low. In
this article, new double-block-length hash functions with higher rates
are presented which are also optimally collision resistant in the blackbox
model. They are composed of block ciphers whose key length is twice
larger than their block length
Analysis of property-preservation capabilities of the ROX and ESh hash domain extenders
Two of the most recent and powerful multi-property preserving (MPP) hash domain extension transforms are the Ramdom-Oracle-XOR (ROX) transform and the Enveloped Shoup (ESh) transform. The former was proposed by Andreeva et al. at ASIACRYPT 2007 and the latter was proposed by Bellare and Ristenpart at ICALP 2007. In the existing literature, ten notions of security for hash functions have been considered in analysis of MPP capabilities of domain extension transforms, namely CR, Sec, aSec, eSec (TCR), Pre, aPre, ePre, MAC, PRF, PRO. Andreeva et al. showed that ROX is able to preserve seven properties; namely collision resistance (CR), three flavors of second preimage resistance (Sec, aSec, eSec) and three variants of preimage resistance (Pre, aPre, ePre). Bellare and Ristenpart showed that ESh is capable of preserving five important security notions; namely CR, message authentication code (MAC), pseudorandom function (PRF), pseudorandom oracle (PRO), and target collision resistance (TCR). Nonetheless, there is no further study on these two MPP hash domain extension transforms with regard to the other properties. The aim of this paper is to fill this gap. Firstly, we show that ROX does not preserve two other widely-used and important security notions, namely MAC and PRO. We also show a positive result about ROX, namely that it also preserves PRF. Secondly, we show that ESh does not preserve other four properties, namely Sec, aSec, Pre, and aPre. On the positive side we show that ESh can preserve ePre property. Our results in this paper provide a full picture of the MPP capabilities of both ROX and ESh transforms by completing the property-preservation analysis of these transforms in regard to all ten security notions of interest, namely CR, Sec, aSec, eSec (TCR), Pre, aPre, ePre, MAC, PRF, PRO
Query Racing: Fast Completeness Certification of Query Results
International audienceWe present a general and effective method to certify completeness of query results on relational tables stored in an untrusted DBMS. Our main contribution is the concept of "Query Race": we split up a general query into several single attribute queries, and exploit concurrency and speed to bind the complexity to the fastest of them. Our method supports selection queries with general composition of conjunctive and disjunctive order-based conditions on different attributes at the same time. To achieve our results, we require neither previous knowledge of queries nor specific support by the DBMS. We validate our approach with experimental results performed on a prototypical implementation
Analysis of the Karmarkar-Karp Differencing Algorithm
The Karmarkar-Karp differencing algorithm is the best known polynomial time
heuristic for the number partitioning problem, fundamental in both theoretical
computer science and statistical physics. We analyze the performance of the
differencing algorithm on random instances by mapping it to a nonlinear rate
equation. Our analysis reveals strong finite size effects that explain why the
precise asymptotics of the differencing solution is hard to establish by
simulations. The asymptotic series emerging from the rate equation satisfies
all known bounds on the Karmarkar-Karp algorithm and projects a scaling
, where . Our calculations reveal subtle
relations between the algorithm and Fibonacci-like sequences, and we establish
an explicit identity to that effect.Comment: 9 pages, 8 figures; minor change
ARMADILLO: A Multi-purpose Cryptographic Primitive Dedicated to Hardware
This paper describes and analyzes the security of a general-purpose cryptographic function design, with application in RFID tags and sensor networks. Based on these analyzes, we suggest minimum parameter values for the main components of this cryptographic function, called ARMADILLO. With fully serial architecture we obtain that 2 923 GE could perform one compression function computation within 176 clock cycles, consuming 44 μW at 1 MHz clock frequency. This could either authenticate a peer or hash 48 bits, or encrypt 128 bits on RFID tags. A better tradeoff would use 4 030 GE, 77 μW of power and 44 cycles for the same, to hash (resp. encrypt) at a rate of 1.1 Mbps (resp. 2.9 Mbps). As other tradeoffs are proposed, we show that ARMADILLO offers competitive performances for hashing relative to a fair Figure Of Merit (FOM)
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