International Association for Cryptologic Research

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09:17 [Pub][ePrint] A provable secure anonymous proxy signature scheme without random oracles, by Rahim Toluee, Maryam Rajabzadeh Asaar, Mahmoud Salmasizadeh

  In order to protect the proxy signers\' privacy, many anonymous proxy signature schemes which are also called proxy ring signatures, have been proposed. Although the provable security in the random oracle model has received a lot of criticism, there is no provable secure anonymous proxy signature scheme without random oracles. In this paper, we propose the first provable secure anonymous proxy signature scheme without random oracles which is the combination of proxy signature and ring signa-ture. For the security analysis, we categorize the adversaries into three types accord-ing to different resources they can get and prove in the standard model that, our pro-posal is anonymous against full key exposure and existential unforgeable against all kinds of adversaries with the computational Diffie-Hellman and the subgroup hiding assumptions in bilinear groups.

04:47 [Event][New] SEC 2014: 29th IFIP TC11 SEC 2014 Int Conf ICT Systems Security & Privacy Protection

  Submission: 20 January 2014
Notification: 10 March 2014
From June 2 to June 4
Location: Marrakech, Morocco
More Information:

04:46 [Event][New] CHES 2014: Cryptographic Hardware and Embedded Systems

  Submission: 3 March 2014
Notification: 26 May 2014
From September 23 to September 26
Location: Busan, Korea
More Information:

16:30 [Job][New] Two PhD Positions, University of Bristol

  The Government Communications Headquarters (GCHQ) in Cheltenham has agreed in principle to sponsor two PhD/Doctoral Studentships at Bristol University in the area of Cryptography. See the link below for the two project descriptions.

The studentships are only open to UK nationals and the successful candidate will be required to spend in the region of 2 - 4 weeks per year at GCHQ headquarters in Cheltenham. To be considered for this studentship, candidates must therefore be prepared to undergo GCHQ\\\'s security clearance procedures.

The studentships will be funded for a period of 3.5 years. GCHQ will cover the costs of university fees (currently £ 3828 per annum) and will provide an annual stipend to the student corresponding to the National Minimum Stipend (currently £ 13,590 per annum) plus an additional stipend of £ 7,000 per annum. Making a total tax-free stipend of £ 20,590 per annum. A generous travel budget is also provided to enable attendance at international conferences and workshops.

08:41 [News] Deadline for Nominations of IACR Fellows

  Nominations and endorsements for IACR Fellows are due on December 31. Instructions are available at

13:03 [Job][New] Two Post-Docs, Nanyang Technological University, Singapore

  We are looking for two Post-Docs in coding and lattice based cryptography. Contact us if you have (or will have soon) a PhD in Cryptography or a related subject, an excellent publication record and would like to work in a fun environment in Singapore.

More information on Coding and Crypto Research Group at Nanyang Technological University can be found at

The applications will be considered immediately. The positions are for 1 year, but renewable up to 3 years.

18:17 [Pub][ePrint] Direct Chosen-Ciphertext Secure Attribute-Based Key Encapsulations without Random Oracles, by Johannes Blömer and Gennadij Liske

  We present a new technique to realize attribute-based encryption (ABE) schemes secure in the standard model against chosen-ciphertext attacks (CCA-secure). Our approach is to extend certain concrete chosen-plaintext secure (CPA-secure) ABE schemes to achieve more efficient constructions than the known generic constructions of CCA-secure ABE schemes. We restrict ourselves to the construction of attribute-based key encapsulation mechanisms (KEMs) and present two concrete CCA-secure schemes: a key-policy attribute-based KEM that is based on Goyal\'s key-policy ABE and a ciphertext-policy attribute-based KEM that is based on Waters\' ciphertext-policy ABE. To achieve our goals, we use an appropriate hash function and need to extend the public parameters and the ciphertexts of the underlying CPA-secure encryption schemes only by a single group element. Moreover, we use the same hardness assumptions as the underlying CPA-secure encryption schemes.

18:17 [Pub][ePrint] A note on high-security general-purpose elliptic curves, by Diego F. Aranha and Paulo S. L. M. Barreto and Geovandro C. C. F. Pereira

  In this note we describe some general-purpose, high-efficiency elliptic curves targeting at security levels beyond $2^{128}$. As a bonus, we also include legacy-level curves. The choice was made to facilitate state-of-the-art implementation techniques.

15:17 [Pub][ePrint] Communication-Efficient MPC for General Adversary Structures, by Joshua Lampkins and Rafail Ostrovsky

  A multiparty computation (MPC) protocol allows a set of players to compute a function of their inputs while keeping the inputs private and at the same time securing the correctness of the output. Most MPC protocols assume that the adversary can corrupt up to a fixed fraction of the number of players. Hirt and Maurer initiated the study of MPC under more general corruption patterns, in which the adversary is allowed to corrupt any set of players in some pre-defined collection of sets [6]. In this paper we consider this important direction of research and present significantly improved communication complexity of MPC protocols for general adversary structures. More specifically, ours is the first unconditionally secure protocol that achieves linear communication in the size of Monotone Span Program representing the adversary structure in the malicious setting against any Q2 adversary structure, whereas all previous protocols were at least cubic.

15:17 [Pub][ePrint] Indistinguishability Obfuscation vs. Auxiliary-Input Extractable Functions: One Must Fall, by Nir Bitansky and Ran Canetti and Omer Paneth and Alon Rosen

  We show that if there exist indistinguishability obfuscators for all circuits then there do not exist auxiliary-input extractable one-way functions. In particular, the knowledge of exponent assumption with

respect to adversaries with auxiliary input is false in any group where computing discrete logarithms is intractable. The proof uses the \"punctured programs\" technique of [Sahai-Waters 2013].

15:17 [Pub][ePrint] Multiparty Key Exchange, Efficient Traitor Tracing, and More from Indistinguishability Obfuscation, by Dan Boneh and Mark Zhandry

  In this work, we show how to use indistinguishability obfuscation (iO) to build multiparty key exchange, efficient broadcast encryption, and efficient traitor tracing. In addition to being the first constructions of these primitives from iO, our schemes also enjoy several interesting properties that have not been achievable before:

- Our multiparty key exchange protocol does not require a trusted setup. Moreover, the size of the published value from each user is independent of the total number of users.

- Our broadcast encryption schemes support distributed setup, where users choose their own secret keys. The broadcast ciphertext size is independent of the number of users.

- Our traitor tracing system is fully collusion resistant and provides ciphertexts that are logarithmic in the number of users and constant-sized secret keys. This construction resolves an open problem relating to differential privacy.

Our proof of security for traitor tracing introduces a new tool for iO proofs: the construction makes use of a key-homomorphic symmetric cipher which plays a crucial role in the proof of security.