International Association for Cryptologic Research

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2015-01-27
13:17 [Pub][ePrint] More Efficient Oblivious Transfer Extensions with Security for Malicious Adversaries, by Gilad Asharov and Yehuda Lindell and Thomas Schneider and Michael Zohner

  Oblivious transfer (OT) is one of the most fundamental primitives in cryptography and is widely used in protocols for secure two-party and multi-party computation. As secure computation becomes more practical, the need for practical large scale oblivious transfer protocols is becoming more evident. Oblivious transfer extensions are protocols that enable a relatively small number of \"base-OTs\" to be utilized to compute a very large number of OTs at low cost. In the semi-honest setting, Ishai et al. (CRYPTO 2003) presented an OT extension protocol for which the cost of each OT (beyond the base-OTs) is just a few hash function operations. In the malicious setting, Nielsen et al. (CRYPTO 2012) presented an efficient OT extension protocol for the setting of active adversaries, that is secure in the random oracle model.

In this work, we present an OT extension protocol for the setting of malicious adversaries that is more efficient and uses less communication than previous works. In addition, our protocol can be proven secure in both the random oracle model, and in the standard model with a type of correlation robustness. Given the importance of OT in many secure computation protocols, increasing the efficiency of OT extensions is another important step forward to making secure computation practical.



13:17 [Pub][ePrint] Evaluation and Cryptanalysis of the Pandaka Lightweight Cipher, by Yuval Yarom and Gefei Li and Damith C. Ranasinghe

  There is a growing need to develop lightweight cryptographic primitives suitable for resource-constrained devices permeating in increasing numbers into the fabric of life. Such devices are exemplified none more so than by batteryless radio frequency identification (RFID) tags in applications ranging from automatic identification and monitoring to anti-counterfeiting. Pandaka is a lightweight cipher together with a protocol proposed in INFOCOM 2014 for extremely resource limited RFID tags. It is designed to reduce the hardware cost (area of silicon) required for implementing the cipher by shifting the computationally intensive task of cryptographically secure random number generation to the reader. In this paper we evaluate Pandaka and demonstrate that the communication protocol contains flaws which completely break the security of the cipher and make Pandaka susceptible to de-synchronisation. Furthermore, we show that, even without the protocol flaws, we can use a guess and determine method to mount an attack on the cipher for the more challenging scenario of a known-plaintext attack with an expected complexity of only $2^{55}$. We conclude that Pandaka needs to be amended and highlight simple measures to prevent the above attacks.



02:35 [Event][New] Cyber Security in the Critical Infrastructure: Advances and Future Direction

  Submission: 31 August 2015
From January 1 to August 31
More Information: http://www.journals.elsevier.com/journal-of-computer-and-system-sciences/call-for-papers/cyber-security-in-the-crit


02:28 [Event][New] Cloud Cryptography: State of the Art and Recent Advances

  Submission: 1 May 2015
Notification: 1 October 2015
From January 1 to May 1
More Information: http://www.journals.elsevier.com/future-generation-computer-systems/call-for-papers/special-issue-on-cloud-cryptogr




2015-01-26
23:57 [Job][New] 1 PhD student, 2 Postdocs , Graz University of Technology

  Graz University of Technology employs about 60 researchers in the area of information security. We are currently expanding our research team and we are looking for two postdocs and one PhD student in the following fields of research:

  • Leakage-resilient cryptography
  • Side-channel and fault attacks
  • System security
  • Secure processor design
  • Verification tools and compilers for security

In case you are interested in pursuing a PhD in one of the fields or in joining our team as a postdoc, please send an application by email to Stefan Mangard.

The application should include a curriculum vitae, a statement of motivation, a transcript of records as well as names and email addresses of two persons that can provide references. More information on our research topics and our team can be found on our group website - see link below.



16:17 [Pub][ePrint] Cold Boot Attacks in the Discrete Logarithm Setting, by Bertram Poettering and Dale L. Sibborn

  In a cold boot attack a cryptosystem is compromised by analysing a noisy version of its internal state. For instance, if a computer is rebooted the memory contents are rarely fully reset; instead, after the reboot an adversary might recover a noisy image of the old memory contents and use it as a stepping stone for reconstructing secret keys. While such attacks were known for a long time, they recently experienced a revival in the academic literature. Here, typically either RSA-based schemes or blockciphers are targeted.

We observe that essentially no work on cold boot attacks on schemes defined in the discrete logarithm setting (DL) and particularly for elliptic curve cryptography (ECC) has been conducted. In this paper we hence consider cold boot attacks on selected wide-spread implementations of DL-based cryptography. We first introduce a generic framework to analyse cold boot settings and construct corresponding key-recovery algorithms. We then study common in-memory encodings of secret keys (in particular those of the wNAF-based and comb-based ECC implementations used in OpenSSL and PolarSSL, respectively), identify how redundancies can be exploited to make cold boot attacks effective, and develop efficient dedicated key-recovery algorithms. We complete our work by providing theoretical bounds for the success probability of our attacks.



16:17 [Pub][ePrint] Universally Verifiable Multiparty Computation from Threshold Homomorphic Cryptosystems, by Berry Schoenmakers and Meilof Veeningen

  Multiparty computation can be used for privacy-friendly outsourcing of computations on private inputs of multiple parties. A computation is outsourced to several computation parties; if not too many are corrupted (e.g., no more than half), then they cannot determine the inputs or produce an incorrect output. However, in many cases, these guarantees are not enough: we need correctness even if /all/ computation parties may be corrupted; and we need that correctness can be verified even by parties that did not participate in the computation. Protocols satisfying these additional properties are called ``universally verifiable\'\'. In this paper, we propose a new security model for universally verifiable multiparty computation, and we present a practical construction, based on a threshold homomorphic cryptosystem. We also develop a multiparty protocol for jointly producing non-interactive zero-knowledge proofs, which may be of independent interest.



16:17 [Pub][ePrint] Security of Symmetric Encryption in the Presence of Ciphertext Fragmentation, by Alexandra Boldyreva and Jean Paul Degabriele and Kenneth G. Paterson and Martijn Stam

  In recent years, a number of standardized symmetric encryption schemes

have fallen foul of attacks exploiting the fact that in some real world scenarios ciphertexts can be delivered in a fragmented fashion. We initiate the first general and formal study of the security of symmetric encryption against such attacks. We extend the SSH-specific work of Paterson and Watson (Eurocrypt 2010) to develop security models for the fragmented setting. We also develop security models to formalize the additional desirable properties of ciphertext boundary hiding and robustness against Denial-of-Service (DoS) attacks for schemes in this setting. We illustrate the utility of each of our models via efficient constructions for schemes using only standard cryptographic components, including constructions that simultaneously achieve confidentiality, ciphertext boundary hiding and DoS robustness.





2015-01-24
02:17 [Job][New] 2 x Lectureships (equivalent to assistant professor) in Security of Cyber-Physical Systems, Security Lancaster Research Centre, Lancaster University, UK

  Cyber-physical systems (CPS) present the new frontier for security. The number of connected devices is expected to grow to 50 billion by the year 2020. This growth is being driven by innovations in the areas of smart cities, internet of things, body-area networks (in healthcare), smart grids and wearable sensors. With digital technologies becoming embedded in everyday objects and infrastructures, CPS offer both great opportunities and great problems of security for modern society. They raise major research challenges with regards to security of the data and information, the systems and infrastructures and the users interacting with them on a daily basis. The research agendas raised by these questions are interdisciplinary and can be tackled from a range of technical, behavioural and socio-economic perspectives. The proposed position will, therefore, be based in Security Lancaster, our inter-disciplinary research centre on Security and Protection Science.

Security Lancaster is one of only four flagship Lancaster Research Centres and was amongst the first 8 Academic Centres of Excellence in Cyber Security Research recognised by the UK government. With over 70 researchers, it is one of the few multi-disciplinary centres to tackle human and technological challenges to cyber security by integrating computer science researchers with expertise from social and behavioural sciences. The centre has a thriving PhD programme with over 30 current graduate students engaged in security research.

For these posts (equivalent to Assistant Professor) we are seeking a ‘rising star’ in security of cyber-physical systems, with a strong and growing international reputation, evidenced by excellent international publications in leading security journals and conferences.





2015-01-23
16:17 [Pub][ePrint] Non-committing encryption from $\\Phi$-hiding, by Brett Hemenway and Rafail Ostrovsky and Alon Rosen

  A multiparty computation protocol is said to be adaptively secure if it retains its security even in the presence of an adversary who can corrupt

participants as the protocol proceeds. This is in contrast to the static corruption model where the adversary is forced to choose which participants

to corrupt before the protocol begins.

A central tool for constructing adaptively secure protocols is non-committing encryption (Canetti, Feige, Goldreich and Naor, STOC \'96). The

original protocol of Canetti et al. had ciphertext expansion that was quadratic in the security parameter, and prior to this work, the

best known constructions had ciphertext expansion that was linear in the security parameter.

In this work, we present the first non-committing encryption scheme that achieves ciphertext expansion that is logarithmic in the message length.

Our construction has optimal round complexity (2-rounds), where (just as in all previous constructions) the first message consists of a public-key

of size $\\tilde{\\bigoh}(n \\secpar)$ where $n$ is the message length and $\\secpar$ is the security parameter. The second message consists

of a ciphertext of size $\\bigoh( n \\log n + \\secpar )$. The security of our scheme is proved based on the $\\Phi$-hiding problem.



16:17 [Pub][ePrint] Richer Efficiency/Security Trade-offs in 2PC, by Vladimir Kolesnikov and Payman Mohassel and Ben Riva and Mike Rosulek

  The dual-execution protocol of Mohassel \\& Franklin (PKC 2006) is a highly efficient (each party garbling only one circuit) 2PC protocol that achieves malicious security apart from leaking an {\\em arbitrary, adversarially-chosen} predicate about the honest party\'s input. We present two practical and orthogonal approaches to improve the security of the dual-execution technique.

First, we show how to greatly restrict the predicate that an adversary can learn in the protocol, to a natural notion of ``only computation leaks\'\'-style leakage. Along the way, we identify a natural security property of garbled circuits called {\\em property-enforcing} that may be of independent interest.

Second, we address a complementary direction of reducing the probability that the leakage occurs. We propose a new dual-execution protocol --- with a very light cheating-detection phase and each party garbling $s+1$ circuits --- in which a cheating party learns a bit with probability only $2^{-s}$. Our concrete measurements show approximately $35\\%$ reduction in communication for the AES circuit, compared to the best combination of state of the art techniques for achieving the same security notion.

Combining the two results, we achieve a rich continuum of practical trade-offs between efficiency \\& security, connecting the covert, dual-execution and full-malicious guarantees.