756 research outputs found
A Framework for Evaluating Security in the Presence of Signal Injection Attacks
Sensors are embedded in security-critical applications from medical devices
to nuclear power plants, but their outputs can be spoofed through
electromagnetic and other types of signals transmitted by attackers at a
distance. To address the lack of a unifying framework for evaluating the
effects of such transmissions, we introduce a system and threat model for
signal injection attacks. We further define the concepts of existential,
selective, and universal security, which address attacker goals from mere
disruptions of the sensor readings to precise waveform injections. Moreover, we
introduce an algorithm which allows circuit designers to concretely calculate
the security level of real systems. Finally, we apply our definitions and
algorithm in practice using measurements of injections against a smartphone
microphone, and analyze the demodulation characteristics of commercial
Analog-to-Digital Converters (ADCs). Overall, our work highlights the
importance of evaluating the susceptibility of systems against signal injection
attacks, and introduces both the terminology and the methodology to do so.Comment: This article is the extended technical report version of the paper
presented at ESORICS 2019, 24th European Symposium on Research in Computer
Security (ESORICS), Luxembourg, Luxembourg, September 201
Almost Perfect Privacy for Additive Gaussian Privacy Filters
We study the maximal mutual information about a random variable
(representing non-private information) displayed through an additive Gaussian
channel when guaranteeing that only bits of information is leaked
about a random variable (representing private information) that is
correlated with . Denoting this quantity by , we show that
for perfect privacy, i.e., , one has for any pair of
absolutely continuous random variables and then derive a second-order
approximation for for small . This approximation is
shown to be related to the strong data processing inequality for mutual
information under suitable conditions on the joint distribution . Next,
motivated by an operational interpretation of data privacy, we formulate the
privacy-utility tradeoff in the same setup using estimation-theoretic
quantities and obtain explicit bounds for this tradeoff when is
sufficiently small using the approximation formula derived for
.Comment: 20 pages. To appear in Springer-Verla
Securing computation against continuous leakage
30th Annual Cryptology Conference, Santa Barbara, CA, USA, August 15-19, 2010. ProceedingsWe present a general method to compile any cryptographic algorithm into one which resists side channel attacks of the only computation leaks information variety for an unbounded number of executions. Our method uses as a building block a semantically secure subsidiary bit encryption scheme with the following additional operations: key refreshing, oblivious generation of cipher texts, leakage resilience re-generation, and blinded homomorphic evaluation of one single complete gate (e.g. NAND). Furthermore, the security properties of the subsidiary encryption scheme should withstand bounded leakage incurred while performing each of the above operations.
We show how to implement such a subsidiary encryption scheme under the DDH intractability assumption and the existence of a simple secure hardware component. The hardware component is independent of the encryption scheme secret key. The subsidiary encryption scheme resists leakage attacks where the leakage is computable in polynomial time and of length bounded by a constant fraction of the security parameter.Israel Science Foundation (710267)United States-Israel Binational Science Foundation (710613)National Science Foundation (U.S.) (6914349)Weizmann KAMAR Gran
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Transcriptional Regulation of Human and Rat Hepatic Lipid Metabolism by the Grapefruit Flavonoid Naringenin: Role of PPARα, PPARγ and LXRα
Disruption of lipid and carbohydrate homeostasis is an important factor in the development of prevalent metabolic diseases such as diabetes, obesity, and atherosclerosis. Therefore, small molecules that could reduce insulin dependence and regulate dyslipidemia could have a dramatic effect on public health. The grapefruit flavonoid naringenin has been shown to normalize lipids in diabetes and hypercholesterolemia, as well as inhibit the production of HCV. Here, we demonstrate that naringenin regulates the activity of nuclear receptors PPARα, PPARγ, and LXRα. We show it activates the ligand-binding domain of both PPARα and PPARγ, while inhibiting LXRα in GAL4-fusion reporters. Using TR-FRET, we show that naringenin is a partial agonist of LXRα, inhibiting its association with Trap220 co-activator in the presence of TO901317. In addition, naringenin induces the expression of PPARα co-activator, PGC1α. The flavonoid activates PPAR response element (PPRE) while suppressing LXRα response element (LXRE) in human hepatocytes, translating into the induction of PPAR-regulated fatty acid oxidation genes such as CYP4A11, ACOX, UCP1 and ApoAI, and inhibition of LXRα-regulated lipogenesis genes, such as FAS, ABCA1, ABCG1, and HMGR. This effect results in the induction of a fasted-like state in primary rat hepatocytes in which fatty acid oxidation increases, while cholesterol and bile acid production decreases. Our findings explain the myriad effects of naringenin and support its continued clinical development. Of note, this is the first description of a non-toxic, naturally occurring LXRα inhibitor
Circular and leakage resilient public-key encryption under subgroup indistinguishability (or: Quadratic residuosity strikes back)
30th Annual Cryptology Conference, Santa Barbara, CA, USA, August 15-19, 2010. ProceedingsThe main results of this work are new public-key encryption schemes that, under the quadratic residuosity (QR) assumption (or Paillierâs decisional composite residuosity (DCR) assumption), achieve key-dependent message security as well as high resilience to secret key leakage and high resilience to the presence of auxiliary input information.
In particular, under what we call the subgroup indistinguishability assumption, of which the QR and DCR are special cases, we can construct a scheme that has:
âą Key-dependent message (circular) security. Achieves security even when encrypting affine functions of its own secret key (in fact, w.r.t. affine âkey-cyclesâ of predefined length). Our scheme also meets the requirements for extending key-dependent message security to broader classes of functions beyond affine functions using previous techniques of Brakerski et al. or Barak et al.
âą Leakage resiliency. Remains secure even if any adversarial low-entropy (efficiently computable) function of the secret key is given to the adversary. A proper selection of parameters allows for a âleakage rateâ of (1âââo(1)) of the length of the secret key.
âą Auxiliary-input security. Remains secure even if any sufficiently hard to invert (efficiently computable) function of the secret key is given to the adversary.
Our scheme is the first to achieve key-dependent security and auxiliary-input security based on the DCR and QR assumptions. Previous schemes that achieved these properties relied either on the DDH or LWE assumptions. The proposed scheme is also the first to achieve leakage resiliency for leakage rate (1âââo(1)) of the secret key length, under the QR assumption. We note that leakage resilient schemes under the DCR and the QR assumptions, for the restricted case of composite modulus product of safe primes, were implied by the work of Naor and Segev, using hash proof systems. However, under the QR assumption, known constructions of hash proof systems only yield a leakage rate of o(1) of the secret key length.Microsoft Researc
Experimental quantum tossing of a single coin
The cryptographic protocol of coin tossing consists of two parties, Alice and
Bob, that do not trust each other, but want to generate a random bit. If the
parties use a classical communication channel and have unlimited computational
resources, one of them can always cheat perfectly. Here we analyze in detail
how the performance of a quantum coin tossing experiment should be compared to
classical protocols, taking into account the inevitable experimental
imperfections. We then report an all-optical fiber experiment in which a single
coin is tossed whose randomness is higher than achievable by any classical
protocol and present some easily realisable cheating strategies by Alice and
Bob.Comment: 13 page
Algorithmic Tamper-Proof (ATP) Security: Theoretical Foundations for Security against Hardware Tampering
Abstract. Traditionally, secure cryptographic algorithms provide security against an adversary who has only black-box access to the secret information of honest parties. However, such models are not always adequate. In particular, the security of these algorithms may completely break under (feasible) attacks that tamper with the secret key. In this paper we propose a theoretical framework to investigate the algorithmic aspects related to tamper-proof security. In particular, we define a model of security against an adversary who is allowed to apply arbitrary feasible functions f to the secret key sk, and obtain the result of the cryptographic algorithms using the new secret key f(sk). We prove that in the most general setting it is impossible to achieve this strong notion of security. We then show minimal additions to the model, which are needed in order to obtain provable security. We prove that these additions are necessary and also sufficient for most common cryptographic primitives, such as encryption and signature schemes. We discuss the applications to portable devices protected by PINs and show how to integrate PIN security into the generic security design. Finally we investigate restrictions of the model in which the tampering powers of the adversary are limited. These restrictions model realistic attacks (like differential fault analysis) that have been demonstrated in practice. In these settings we show security solutions that work even without the additions mentioned above
Searching a bitstream in linear time for the longest substring of any given density
Given an arbitrary bitstream, we consider the problem of finding the longest
substring whose ratio of ones to zeroes equals a given value. The central
result of this paper is an algorithm that solves this problem in linear time.
The method involves (i) reformulating the problem as a constrained walk through
a sparse matrix, and then (ii) developing a data structure for this sparse
matrix that allows us to perform each step of the walk in amortised constant
time. We also give a linear time algorithm to find the longest substring whose
ratio of ones to zeroes is bounded below by a given value. Both problems have
practical relevance to cryptography and bioinformatics.Comment: 22 pages, 19 figures; v2: minor edits and enhancement
Leakage-resilient coin tossing
Proceedings 25th International Symposium, DISC 2011, Rome, Italy, September 20-22, 2011.The ability to collectively toss a common coin among n parties
in the presence of faults is an important primitive in the arsenal of
randomized distributed protocols. In the case of dishonest majority, it
was shown to be impossible to achieve less than 1
r bias in O(r) rounds
(Cleve STOC â86). In the case of honest majority, in contrast, unconditionally
secure O(1)-round protocols for generating common unbiased
coins follow from general completeness theorems on multi-party secure
protocols in the secure channels model (e.g., BGW, CCD STOC â88).
However, in the O(1)-round protocols with honest majority, parties
generate and hold secret values which are assumed to be perfectly hidden
from malicious parties: an assumption which is crucial to proving the
resulting common coin is unbiased. This assumption unfortunately does
not seem to hold in practice, as attackers can launch side-channel attacks
on the local state of honest parties and leak information on their secrets.
In this work, we present an O(1)-round protocol for collectively generating
an unbiased common coin, in the presence of leakage on the local
state of the honest parties. We tolerate t †( 1
3
â )n computationallyunbounded
Byzantine faults and in addition a Ω(1)-fraction leakage on
each (honest) partyâs secret state. Our results hold in the memory leakage
model (of Akavia, Goldwasser, Vaikuntanathan â08) adapted to the
distributed setting.
Additional contributions of our work are the tools we introduce to
achieve the collective coin toss: a procedure for disjoint committee election,
and leakage-resilient verifiable secret sharing.National Defense Science and Engineering Graduate FellowshipNational Science Foundation (U.S.) (CCF-1018064
All Languages in NP Have Divertible Zero-Knowledge Proofs and Arguments Under Cryptographic Assumptions
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