*04:17* [Pub][ePrint]
Efficient, Oblivious Data Structures for MPC, by Marcel Keller and Peter Scholl
We present oblivious implementations of several data structures for secure multiparty computation (MPC) such as arrays, dictionaries, and priority queues. The resulting oblivious data structures have only polylogarithmic overhead compared with their classical counterparts. To achieve this, we give secure multiparty protocols for the ORAM of Shi et al. (Asiacrypt `11) and the Path ORAM scheme of van Dijk et al. (CCS `13), and we compare the resulting implementations. We subsequently use our oblivious priority queue for secure computation of Dijkstra\'s shortest path algorithm on general graphs, where the graph structure is secret. To the best of our knowledge, this is the first implementation of a non-trivial graph algorithm in multiparty computation with polylogarithmic overhead.We implemented and benchmarked all of our protocols using the SPDZ protocol of Damgaard et al. (Crypto `12), which works in the preprocessing model and ensures active security against an adversary corrupting all but one players. For two parties, the access time for an oblivious array of size 1 million is under 250 ms.

*04:17* [Pub][ePrint]
Short Signatures from Diffie-Hellman, Revisited: Sublinear Public Key, CMA Security, and Tighter Reduction, by Jae Hong Seo
Designing practical signature scheme based on the standard assumption such as the Computational Diffie-Hellman (CDH) assumption is important both from a practical and a theoretical point of view. Currently, there are only three standard model CDH-based signature schemes with short signatures due to Waters (EUROCRYPT 2005), Seo, and B\\\"ohl et al. (the merged paper in EUROCRYPT 2013). The Waters signature scheme achieves the Existentail UnForgeability against Chosen Message Attack (EUF-CMA) with nearly optimal reduction. However, this scheme suffers from large public keys. To shorten public key size, Seo and B\\\"ohl et al. proposed new approaches, respectively, but each approach has a weak point rather than the Waters signature scheme; Seo\'s approach could prove only a rather weak security, called the bounded CMA security, and B\\\"ohl et al.\'s approach inherently accompanies a loose reduction. In this paper, we aim at stepping towards practical EUF-CMA secure signatures with tighter reduction; that is, we achieve sublinear public keys with preserving the same security as the Waters signatures. To this end, we revisit the Seo signature scheme and devise an alternative and simple analysis leading the standard EUF-CMA security with tighter reduction. In particular, our security proof has a reduction loss of $O(\\lambda q)$, which is less than $O(\\sqrt{\\frac{\\lambda}{\\log}}\\lambda q)$ of the original security proof, where $\\lambda$ is the security parameter, and is almost the same as that of the Water signature scheme.

*15:48* [Job][New]
Lecturer/Associate Professor/Researcher in Cryptology and Security, *Hangzhou Normal University, China, Pacific Area*
The group for Cryptography and Network Security at Hangzhou Normal University, China chaired by Prof. Dr. Qi Xie is looking for two faculty members with strong crypto/security background. Candidates should have a PhD degree in mathematics, computer science, or related disciplines, be highly motivated with strong R&D capability and also a good team player, have good presentation and communication skills, be able to perform deep system-level investigations of security mechanisms. The candidates are expected to publish high-quality papers OR develop security-related projects. Any prior experience in e-health or WSN/VANETs security is certainly an asset..Interested candidates please send CV to Shengbao Wang {shengbaowang (at) hznu.edu.cn}. The positions offer a competitive salary. All candidates will be contacted for further infomation.

*16:17* [Pub][ePrint]
A Note on the CLRW2 Tweakable Block Cipher Construction, by Gordon Procter
In this note, we describe an error in the proof for CLRW2 given by Landecker et al. in their paper at CRYPTO 2012 on the beyond-birthday-bound security for tweakable block ciphers.We are able to resolve the issue, give a new bound for the security of CLRW2, and identify a potential limitation of this proof technique when looking to extend the scheme to provide asymptotic security.