International Association for Cryptologic Research

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2013-06-25
18:17 [Pub][ePrint] Policy-Based Signatures, by Mihir Bellare and Georg Fuchsbauer

  We introduce signatures where signers can only sign messages that conform to some policy, yet privacy of the policy is maintained. We provide definitions and show that policy-based signatures provide a framework which yields a unified view of many other existing types of signatures that now appear as special cases. We also show how still other primitives are easily realized using policy-based signatures as a building block. We provide generic constructions of policy-based signatures and then show how to achieve them efficiently.



18:17 [Pub][ePrint] A novel certificateless deniable authentication protocol, by Chunhua Jin, Chunxiang Xu, Xiaojun Zhang, Qianna Xie, Fagen Li

  Deniable authenticated protocol is a new and attractive protocol compared to the traditional authentication protocol. It allows the appointed receiver to identify the source of a given message, but not to prove the identity of the sender to a third party even if the appointed receiver is willing to reveal its private key. In this paper, we first define a security model for certificateless deniable authentication protocols. Then we propose a non-interactive certificateless deniable authentication protocol, by combining deniable authentication protocol with certificateless cryptography. In addition, we prove its security in the random oracle model.



18:17 [Pub][ePrint] Short collision search in arbitrary SL2 homomorphic hash functions, by Ciaran Mullan and Boaz Tsaban

  We study homomorphic hash functions into SL2(q), the 2x2 matrices with determinant 1 over the

field with q elements.

Modulo a well supported number theoretic hypothesis, which holds in particular for all concrete

homomorphisms proposed thus far, we prove that

a random homomorphism is at least as secure as any concrete homomorphism.

For a family of homomorphisms containing several concrete proposals in the literature,

we prove that collisions of length O(log q) can be found in running time O(sqrt q).

For general homomorphisms we offer an algorithm that, heuristically and according to experiments,

in running time O(sqrt q) finds collisions of length O(log q) for q even, and length O(log^2 q/loglog q) for arbitrary q.

For any conceivable practical scenario, our algorithms are substantially faster than all earlier algorithms

and produce much shorter collisions.



18:17 [Pub][ePrint] Computational Fuzzy Extractors, by Benjamin Fuller and Xianrui Meng and Leonid Reyzin

  Fuzzy extractors derive strong keys from noisy sources. Their security is defined information- theoretically, which limits the length of the derived key, sometimes making it too short to be useful. We ask whether it is possible to obtain longer keys by considering computational security, and show the following.

-Negative Result: Noise tolerance in fuzzy extractors is usually achieved using an information reconciliation component called a \"secure sketch.\" The security of this component, which directly affects the length of the resulting key, is subject to lower bounds from coding theory. We show that, even when defined computationally, secure sketches are still subject to lower bounds from coding theory. Specifically, we consider two computational relaxations of the information-theoretic security requirement of secure sketches, using conditional HILL entropy and unpredictability entropy. For both cases we show that computational secure sketches cannot outperform the best information-theoretic secure sketches in the case of high-entropy Hamming metric sources.

-Positive Result: We show that the negative result can be overcome by analyzing computational fuzzy extractors directly. Namely, we show how to build a computational fuzzy extractor whose output key length equals the entropy of the source (this is impossible in the information-theoretic setting). Our construction is based on the hardness of the Learning with Errors (LWE) problem, and is secure when the noisy source is uniform or symbol-fixing (that is, each dimension is either uniform or fixed). As part of the security proof, we show a result of independent interest, namely that the decision version of LWE is secure even when a small number of dimensions has no error.



18:17 [Pub][ePrint] The Improved Cube Attack on Grain-v1, by Yongjuan Wang and Liren Ding and Wenbao Han and Xiangyu Wang

  The crucial problem of cube attack is the selection of cube set, which also being the most time-consuming process. This paper designs a new search algorithm which generates several linear equations through one cube set and applies cube attack to simplified version of Grain-v1algorithem. Our attack directly recovers 14 bits of the secret key when the initialization rounds in Grain-v1is 75 and finds 5 linear expressions about another 28 bits of the key.



18:17 [Pub][ePrint] Unconditional Tightness Bounds for Generic Reductions: The Exact Security of Schnorr Signatures, Revisited, by Nils Fleischhacker and Tibor Jager and Dominique Schröder

  A long line of research investigates the existence of tight security reductions for the Schnorr signature scheme. Most of these works presented lower tightness bounds, most recently Seurin (Eurocrypt 2012) showed that under certain assumptions the non-tight security proof for Schnorr signatures by Pointcheval and Stern (Eurocrypt 1996) is essentially optimal. All previous works in this direction share the same restrictions: The results hold only under the interactive one-more discrete logarithm assumption, they only consider algebraic reductions, and they only rule out tight reductions from the (one-more) discrete logarithm problem. The existence of a tight reduction from weaker computational problems, like CDH or DDH, remained open.

In this paper we introduce a new meta-reduction technique, which allows to prove lower bounds for the large and very natural class of generic reductions. A generic reduction is independent of a particular representation of group elements. Most reductions in state-of-the-art security proofs have this desirable property. This new approach allows to show unconditionally that there is no tight generic reduction from any natural computational problem \\Pi defined over algebraic groups (including even interactive problems) to breaking Schnorr signatures, unless solving \\Pi is easy.



16:43 [Job][New] Assistant Professor (tenure track), Technische Universiteit Eindhoven

  We are looking for a candidate who meets the following requirements:

  • A PhD degree in Mathematics or Computer Science;

  • Research experience in coding theory or coding theory;

  • Outstanding research achievements and promise for the future;

  • Excellent track record of international publications in leading journals and high-ranked conferences;

  • High potential for the acquisition of external research funds;

  • Readiness to supervise PhD projects;

  • Teaching experience and good teaching skills;

  • Good English speaking and writing skills, and a willingness to learn Dutch (all Master\\\'s and some Bachelor courses are given in English);

  • Basic Teaching Qualification (BKO): if the candidate in question is not in possession of a BKO certificate, he or she is required to meet this requirement within a maximum period of three years.

    The Department of Mathematics and Computer Science of the Eindhoven University of Technology (TU/e) has a vacancy for a Tenure Track Assistant Professor position for five years in the Coding and Crypto group (section Discrete Mathematics, DM).

    The tenure-track nature of the position will be as follows. The successful candidate will first be appointed for a fixed period of five years. Before the start of the contract, the department and the candidate negotiate a list of conditions for successful conversion. If the candidate meets these conditions at the end of the five years, the position becomes permanent; if not, the temporary position is not continued.

16:36 [Event][New] PETShop'13: PETShop: Workshop on Language Support for Privacy Enhancing Technologies

  Submission: 4 August 2013
Notification: 23 August 2013
From November 4 to November 4
Location: Berlin, Germany
More Information: http://forsyte.at/petshop-2013/


12:35 [Event][New] RISC '13: The 5th International Workshop on RFID/IoT Security and Cryptography

  Submission: 13 September 2013
Notification: 11 October 2013
From December 9 to December 11
Location: London, UK
More Information: http://www.icitst.org/Workshops.html




2013-06-24
16:47 [Event][New] SEC@SAC'14: 13th Computer Security track at the 29th ACM Symposium on Applied Computing

  Submission: 13 September 2013
Notification: 15 November 2013
From March 24 to March 28
Location: Gyeongju, Korea
More Information: http://www.dmi.unict.it/~giamp/sac/cfp2014.php


09:17 [Forum] [IACR Publication Reform] Re: two-stage review process by cbw

  We don\'t have space limitations anymore - we can accept any good paper from now on :-) Best, Christopher Orr Wrote: > you are susceptible > to variance (Y should be O(X), IMHO) in the number > of accepted papers, or some decent papers gets > rejected due to lack of space. From: 2013-24-06 09:11:00 (UTC)