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2013-09-04
15:17 [Pub][ePrint] Algebraic Aspects of the Russian Hash Standard GOST R 34.11-2012, by Oleksandr Kazymyrov and Valentyna Kazymyrova

  New GOST R 34.11-2012 standard has been recently selected by the Russian government to replace the old one. The algorithm is based on the hash function Stribog introduced in 2010. The high-level structure of the new hash function is similar to GOST R 34.11-94 with minor modifications. However, the compression function was changed significantly. Such a choice of the compression algorithm has been motivated by the Rjndael due to simplicity and understandable algebraic structure.

In this paper we consider a number of algebraic aspects of the GOST R 34.11. We show how one can express the cipher in AES-like form over the finite field $\\F_{2^8}$, and consider some approaches that can be used for the fast software implementation.



15:17 [Pub][ePrint] Black-Box Obfuscation for d-CNFs, by Zvika Brakerski and Guy N. Rothblum

  We show how to securely obfuscate a new class of functions: {\\em conjunctions of $NC0_d$ circuits}. These are functions of the form $C(x) = \\bigwedge_{i=1}^m C_i(x)$, where each $C_i$ is a boolean $NC0_d$ circuit, whose output bit is only a function of $d = O(1)$ bits of the input $x$. For example, $d$-CNFs, where each clause is a disjunction of at most $d$ variables, are in this class. Given such a function, we produce an obfuscated program that preserves the input-output functionality of the given function, but reveals nothing else. Our construction is based on multilinear maps, and can be instantiated using the recent candidates proposed by Garg, Gentry and Halevi (EUROCRYPT 2013) and by Coron, Lepoint and Tibouchi (CRYPTO 2013).

We prove that the construction is a secure obfuscation in a generic multilinear group model, under the black-box definition of Barak et al.\\ (CRYPTO 2001). Security is based on a new {\\em worst-case} hardness assumption about exponential hardness of the NP-complete problem 3-SAT, the {\\em Bounded Speedup Hypothesis}.

One of the new techniques we introduce is a method for enforcing input consistency, which we call {\\em randomizing sub-assignments}. We hope that this technique can find further application in constructing secure obfuscators.

The family of functions we obfuscate is considerably richer than previous works that consider black-box obfuscation. As one application, we show how to achieve {\\em obfuscated functional point testing}: namely, to construct a circuit that checks whether $f(x)=y$, where $f$ is an arbitrary ``public\'\' polynomial-time computable function, but $y$ is a ``secret\'\' point that is hidden in the obfuscation.



15:17 [Pub][ePrint] Practical approaches to varying network size in combinatorial key predistribution schemes, by Kevin Henry and Maura B. Paterson and Douglas R. Stinson

  Combinatorial key predistribution schemes can provide a practical solution to the problem of distributing symmetric keys to the nodes of a wireless sensor network. Such schemes often inherently suit networks in which the number of nodes belongs to some restricted set of values (such as powers of primes). In a recent paper, Bose, Dey and Mukerjee have suggested that this might pose a problem, since discarding keyrings to suit a smaller network might adversely affect the properties of the scheme.

In this paper we explore this issue, with specific reference to classes of key predistribution schemes based on transversal designs. We demonstrate through experiments that, for a wide range of parameters, randomly removing keyrings in fact has a negligible and largely predictable effect on the parameters of the scheme. In order to facilitate these computations, we provide a new, efficient, generally applicable approach to computing important properties of combinatorial key predistribution schemes.

We also show that the structure of a resolvable transversal design can be exploited to give a deterministic method of removing keyrings to adjust the network size, in such a way that the properties of the resulting scheme are easy to analyse. We show that these schemes have the same asymptotic properties as the transversal design schemes on which they are based, and that for most parameter choices their behaviour is very similar.



15:17 [Pub][ePrint] A Constructive Approach to Functional Encryption, by Christian Matt and Ueli Maurer

  Functional encryption is an important generalization of several types of encryption such as public-key, identity-based, and attribute-based encryption. Numerous different security definitions for functional encryption have been proposed, most of them being rather complex and involving several algorithms. Many of these definitions differ in details such as which algorithm has oracle access to which oracle, while the consequences of specific choices are often unclear. This spans a large space of possible definitions without a consensus on the adequacy of specific points in this space. What a particular definition means and for which applications it is suitable remains unsettled.

To remedy this situation, we propose a novel interpretation of functional encryption, based on the Constructive Cryptography framework, in which a protocol is seen as a construction of an ideal resource with desired properties from a real resource, which is assumed to be available. The resulting ideal resource can then be used as a real resource in other protocols to construct more advanced resources. The real resource we consider here corresponds to a public repository that allows everyone to read its contents. Such repositories are indeed widely available on the internet. Using functional encryption, we construct, as the ideal resource, a repository with fine-grained access control.

Based on this constructive viewpoint, we propose a new security definition, called FA-security, for functional encryption by adequately modifying an established definition, and prove the equivalence to our notion of construction. This gives evidence that FA-security is an appropriate definition. We further consider known impossibility results and examine a weaker security definition. We show that this weaker definition, for which secure schemes exist, is sufficient to construct a repository that restricts the number and order of interactions. This makes explicit how such schemes can be used.



15:17 [Pub][ePrint] Sometimes-Recurse Shuffle: Almost-Random Permutations in Logarithmic Expected Time, by Ben Morris and Phillip Rogaway

  We describe a security-preserving construction of a random permutation of domain size N from a random function, the construction tolerating adversaries asking all N plaintexts, yet employing just \\Theta(lg N) calls, on average, to the one-bit-output random function. The approach is based on card shuffling. The basic idea is to use the \\textit{sometimes-recurse} transformation: lightly shuffle the deck (with some other shuffle), cut the deck, and then recursively shuffle one of the two halves. Our work builds on a recent paper of Ristenpart and Yilek.



15:17 [Pub][ePrint] Preimage attacks on the round-reduced Keccak with the aid of differential cryptanalysis, by Pawel Morawiecki and Josef Pieprzyk and Marian Srebrny and Michal Straus

  In this paper we use differential cryptanalysis to attack the winner of the SHA-3 competition, namely Keccak hash function. Despite more than 6 years of intensive cryptanalysis there have been known only two preimage attacks which reach 3 (or slightly more) rounds. Our 3-round preimage attack improves the complexity of those two existing attacks and it is obtained with a different technique. We also show the partial preimage attack on the 4-round Keccak, exploiting two properties of the linear step of the Keccak-f permutation.



13:32 [Event][New] Crypto 2014

  From August 17 to August 21
Location: Santa Barbara, USA
More Information: http://www.iacr.org/conferences/crypto2014/




2013-09-03
20:48 [Job][New] Junior Professorship in Mobile Security, Ruhr-Universität Bochum, Germany

  The Faculty of Electrical Engineering and Information Technology at the Ruhr-Universität Bochum invites applications for the position of a Junior Professorship for Mobile Security.

The future occupant of the position Mobile Security represents the department in this field in research and teaching. The appointment will be at the rank of an assistant professor.

His/her scientific work should focus on one or more of the following key research areas:

- Security of mobile systems at the hard- or software level

- Security aspects of new application domains (especially cyber-physical systems)

- Reverse engineering of hardware and software systems

- Security aspects of distributed systems

- Secure and dependable software systems

A doctoral degree of outstanding quality and evidence of special aptitude in teaching are just as much required as the willingness to participate in the self-governing bodies of the RUB. Furthermore, we expect the candidate to generally get involved in university processes according to RUB’s mission statement. Beside the specific skills the candidate should have a profound didactical qualification to develop new learning environments such as research oriented teaching.

We expect furthermore readiness to participate in interdisciplinary academic work, willingness and ability to attract external funding, ability to work in teams, and the will to participate in collaborative research.

The Ruhr-Universität Bochum is an equal opportunity employer.

06:30 [Event][New] CS2-2014: First Workshop on Cryptography and Security in Computing Syste

  Submission: 27 October 2013
Notification: 29 November 2013
From January 20 to January 20
Location: Vienna, Austria
More Information: http://www.cs2.deib.polimi.it/




2013-08-30
21:47 [Job][New] UTRCI Research Scientist, Cyber-physical Systems Security , United Technologies Research Centre, Cork - Ireland

  UTRCI seeks candidates with expertise in cyber-physical security, wireless sensor networks and embedded systems to join their Networks & Embedded Systems group in Cork, Ireland. The successful candidates are expected to coordinate and primarily execute R&D activities within international projects on cyber-physical systems security. UTRC is developing capability in cyber-physical security to apply to the full range of UTC (http://www.utc.com) products and programs.

The candidate should have a solid background in vulnerability assessment and thorough knowledge of best practices in countermeasures and design processes for secure systems, for example, encryption, authentication and anomaly detection. A successful candidate would also have a solid background in embedded systems and cyber-physical systems with past experience in applying cyber-physical security concepts to the particular constraints of embedded systems, including scalability of countermeasures. Practical experience in identifying and demonstrating both vulnerabilities and countermeasures is highly desirable for this position.

Candidates should have a proven track record of research (top journals and conferences) in cyber-security or cyber-physical security.

The ideal candidate is a self-starter who works well in an international teaming environment, is extremely well-organized and has excellent interpersonal, leadership and communication skills. Besides technical excellence, an entrepreneurial attitude towards innovation is essential.

The candidate should have a PhD in Computer Science, Electrical and Computer Engineering or related fields, with particular expertise in Cyber-Physical Systems and Wireless Sensor Networks. The candidate should also have a strong international publication record and demonstrated ability to do independent research. Fluency in written and spoken English is required.

21:46 [Job][New] Ph.D.student, Hochschule Furtwangen University, Germany, EEA

  Hochschule Furtwangen University, Germany, Two Full-time Ph.D. Positions

* The Chair for Security in Distributed Systems, computer science Hochschule Furtwangen, Germany, offers two full-time PhD positions

* The position involves research in the area of IT-security within the BMBF project

ProSeCCo \\\'Promotionsvorhaben zur Erarbeitung von Sicherheitserweiterungen für das

Cloud Computing\\\' in cooperation with the Albert-Ludwig University of Freiburg at the \\\'Institut für Informatik und Gesellschaft (IIG) - Telematik\\\' (Prof. Dr.

Günter Müller) and the university of Karlsruhe (KIT) at the \\\'Institut for Kryptographie und Sicherheit (IKS) (Prof. Dr. Jörn Müller-Quade).

The successful candidate is expected to contribute to research in IT-Security and applied cryptography for Cloud Security.

Besides other cloud security related aspects topics of interest for the two open positions are

- application of homomorphic cryptographic primitives for secure cloud storage,

- monitoring- and attestation mechanisms to control information flow between VMs.

* The position is available from November on and is fully funded. The salary scale for both positions is TV-L E13.

The gross income depends on the candidate\\\'s experience level. At the lowest level it corresponds to approx. 40,000 EUR per year.

* Contracts are initially offered for two years. An extension is possible.

* She or he is given the possiblity to carry out a Ph.D.

* The successful candidate should have a Master\\\'s degree in Computer Science, Mathematics, Information Security, or a related field.

Deep Knowledge in cryptography is not a must but an asset.

* The deadline for applications is September 20, 2013. However, late applications will be considered until the position is filled.

Please send your application with reference number 11