International Association for Cryptologic Research

IACR News Central

You can also access the full news archive.

Further sources to find out about changes are CryptoDB, ePrint RSS, ePrint Web, Event calender (iCal).

2015-04-01
15:17 [Pub][ePrint]

Re-Encryption randomized partial checking (RPC) mix nets were introduced by Jakobsson, Juels, and Rivest in 2002 and since then have been employed in prominent modern e-voting systems and in politically binding elections in order to provide verifiable elections in a simple and efficient way. Being one of or even the most used mix nets in practice so far, these mix nets are an interesting and valuable target for rigorous security analysis.

In this paper, we carry out the first formal cryptographic analysis of re-encryption RPC mix nets. We show that these mix nets, with fixes recently proposed by Khazaei and Wikstr{\\\"o}m, provide a good level of verifiability, and more precisely, accountability: cheating mix servers, who try to manipulate the election outcome, are caught with high probability. Moreover, we show that all attacks that would break the privacy of voters\' inputs are caught with a probability of at least $1/4$. In many cases, for example, when penalties are severe or reputation can be lost, adversaries might not be willing to take this risk, and hence, would behave in a way that avoids this risk. Now, for such a class of risk-avoiding\'\' adversaries, we show that re-encryption RPC mix nets provide a good level of privacy, even if only one mix server is honest.

15:17 [Pub][ePrint]

Consider a collection $f$ of polynomials $f_i(x)$, $i=1, \\ldots,s$, with integer coefficients such that polynomials $f_i(x)-f_i(0)$, $i=1, \\ldots,s$, are linearly independent. Denote by $D_m$ the discrepancy for the set of points $\\left(\\frac{f_1(x) \\bmod m}{m},\\ldots,\\frac{f_s(x) \\bmod m}{p^n}\\right)$ for all $x \\in \\{0,1,\\ldots,m\\}$, where $m=p^n$, $n \\in N$, and $p$ is a prime number. We prove that $D_m\\to 0$ as $n\\to\\infty$, and $D_m 15:17 [Pub][ePrint] Security against selective opening attack (SOA) requires that in a multi-user setting, even if an adversary has access to all ciphertexts from users, and adaptively corrupts some fraction of the users by exposing not only their messages but also the random coins, the remaining unopened messages retain their privacy. Recently, Bellare, Waters and Yilek considered SOA-security in the identity-based setting, and presented the first identity-based encryption (IBE) schemes that are proven secure against selective opening chosen plaintext attack (SO-CPA). However, how to achieve SO-CCA security for IBE is still open. In this paper, we introduce a new primitive called extractable IBE, which is a hybrid of one-bit IBE and identity-based key encapsulation mechanism (IB-KEM), and define its IND-ID-CCA security notion. We present a generic construction of SO-CCA secure IBE from an IND-ID-CCA secure extractable IBE with One-Sided Public Openability\'\'(1SPO), a collision-resistant hash function and a strengthened cross-authentication code. Finally, we propose two concrete constructions of extractable 1SPO-IBE schemes, resulting in the first simulation-based SO-CCA secure IBE schemes without random oracles. 15:17 [Pub][ePrint] As potential post-quantum cryptographic schemes, lattice based encryption schemes and linear codes based encryption schemes have received extensive attention in recent years. Though LLL reduction algorithm has been one of the major cryptanalysis techniques for lattice based cryptographic systems, cryptanalysis techniques for linear codes based cryptographic systems are generally scheme specific. In recent years, several important techniques such as Sidelnikov-Shestakov attack and filtration attacks have been developed to crypt-analyze linear codes based encryption schemes. Though most of these cryptanalysis techniques are relatively new, they prove to be very powerful and many systems have been broken using these techniques. Thus it is important to systematically investigate and design linear code based cryptographic systems that are immune against these attacks. This paper proposes linear code based encryption schemes RLCE which share many characteristics with random linear codes. Our analysis shows that the scheme RLCE is secure against existing attacks and we expect that the security of the RLCE scheme is equivalent to the hardness of decoding random linear codes. 15:17 [Pub][ePrint] In 2010, Lindell and Waisbard proposed a private web search scheme for malicious adversaries. At the end of the scheme, each party obtains one search word and query the search engine with the word. We remark that a malicious party could query the search engine with a false word instead of the word obtained. The malicious party can link the true word to its provider if the party publicly complain for the false searching result. To fix this drawback, each party has to broadcast all shares so as to enable every party to recover all search words and query the search engine with all these words. We also remark that there is a very simple method to achieve the same purpose of private shuffle. When a user wants to privately query the search engine with a word, he can choose another n-1 padding words to form a group of$n$words and permute these words randomly. Finally, he queries the search engine with these words. 15:17 [Pub][ePrint] Divisible E-cash has been introduced twenty years ago but no construction is both fully secure in the standard model and efficiently scalable. In this paper, we fill this gap by providing an anonymous divisible E-cash construction with constant-time withdrawal and spending protocols. Moreover, the deposit protocol is constant-time for the merchant, whatever the spent value is. It just has to compute and store$2^l$serial numbers when a value$2^l$is deposited, compared to$2^n$serial numbers whatever the spent amount (where$2^n$is the global value of the coin) in the recent state-of-the-art paper. This makes a very huge difference when coins are spent many times. Our approach follows the classical tree representation for the divisible coin. However we manage to build the values on the nodes in such a way that the elements necessary to recover the serial numbers are common to all the nodes of the same level: this leads to strong unlinkability and anonymity, the strongest security level for divisible E-cash. 2015-03-31 23:25 [Job][New] Oblong Industries Los Angeles, CA, United States Full-Time What would you do: Oblong is looking for a Security Software Engineer responsible for keeping our core product, Mezzanine, secure. This is a high-impact role in charge of enhancing our existing PKI, writing new security related code, auditing existing code and architectures for security flaws, and reviewing new features for security and privacy. You will work closely with many parts of the organization and interact with customers occasionally. Clear communications skills are crucial for this role. Responsibilities: • Develop production-quality code • Architect and develop security requirements for Mezzanine • Take responsibility for current PKI and code • Improve and maintain current Mezzanine security policies and communicate them to other parts of the company • Keep up-to-date with software vulnerabilities and provide and implement recommendations • Evaluate third-party security updates Requirements: • Substantial experience delivering production-quality, security-related code • Fluency in C and C++ programming and at least one scripting language • Proven ability to design security policies and specifications • Excellent written and verbal communications • Good understanding of cryptography (symmetric and asymmetric ciphers) and secure protocols (TLS, SRTP) • Experience with at least one crypto library (e.g. OpenSSL, GnuTLS) • Good knowledge of PKI and certificate standards Nice to have: • Experience working with Open Source projects • DOD 8570 compliant certification such as CISSP, CISM, CISA or equivalent Benefits and perks: • Competitive compensation package of salary and stock options? • Medical, dental, and vision insurance ? • 401K plan • Gourmet lunches 3 days/week 15:39 [Event][New] Submission: 14 April 2015 Notification: 24 April 2015 From June 27 to July 2 Location: New York, USA More Information: http://sesar.di.unimi.it/SPE2015/ 2015-03-27 17:55 [Job][New] The Information Security Group at Royal Holloway, University of London, is seeking to recruit two Marie Sklodowska-Curie Research Fellows in Cryptography to start in September 2015, as part of the ECRYPT-NET project. ECRYPT-NET is a research network of six universities and two companies that intends to develop advanced cryptographic techniques for the Internet of Things and the Cloud, and to create efficient and secure implementations of those techniques on a broad range of platforms. ECRYPT-NET is funded by a prestigious Marie Sklodowska-Curie ITN (Integrated Training Network) grant. The network will educate a group of 15 PhD students with a set of interdisciplinary skills in the areas of mathematics, computer science and electrical engineering. The training will be provided in an international context that include Summer Schools, workshops and internships. Participants are expected to spend at least six months abroad in a network partner or in one of the seven associated companies. We are looking for highly motivated candidates, ideally with background on cryptology and with proven research abilities. Two of the ECRYPT-NET ESR (Early Stage Researcher) positions will be based at the Information Security Group at Royal Holloway, to work on the following projects: (1) Design and analysis of efficient and lightweight authenticated encryption schemes. (2) Secure outsourcing of computation. Marie Curie ITN eligibility criteria apply to both of these positions. Founded in 1990, the Information Security Group at Royal Holloway is a world-leading interdisciplinary research group dedicated to research and education in the area of cyber security, with an extensive and long-standing record of research in cryptography. It has 16 established academics, 11 RAs, and over 50 PhD students. It gained the status of UK Academic Centre of Excellence in Cyber Security Research by EPSRC and GCHQ, and hosts one of the 2015-03-26 12:17 [Pub][ePrint] We show how to provide privacy-preserving (zero-knowledge) answers to order queries on network data that is organized in lists, trees, and partially-ordered sets of bounded dimension. Our methods are efficient and dynamic, in that they allow for updates in the ordering information while also providing for quick and verifiable answers to queries that reveal no information besides the answers to the queries themselves. 12:17 [Pub][ePrint] Scalar multiplication is the most important and expensive operation in elliptic curve cryptosystems. In this paper we improve the efficiency of the Elliptic Net algorithm to compute scalar multiplication by using the equivalence of elliptic nets. The proposed method saves$four\$ multiplications in each iteration loop. Experimental results also indicates that our algorithm will be more efficient than the previously known results in this line.