IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
10 November 2017
Ashwin Jha, Eik List, Kazuhiko Minematsu, Sweta Mishra, Mridul Nandi
ePrint ReportS V Dilip Kumar, Sikhar Patranabis, Jakub Breier, Debdeep Mukhopadhyay, Shivam Bhasin, Anupam Chattopadhyay, Anubhab Baksi
ePrint ReportSikhar Patranabis, Jakub Breier, Debdeep Mukhopadhyay, Shivam Bhasin
ePrint ReportSabyasachi Dey, Santanu Sarkar
ePrint ReportLe Dong, Yongxia Mao
ePrint ReportChristian Cachin, Angelo De Caro, Pedro Moreno-Sanchez, Bj{\"o}rn Tackmann, Marko Vukoli\'{c}
ePrint ReportIn this work, we fill this gap, motivated by the observation that the semantics of transactions in blockchain systems can be captured by a directed acyclic graph. Such a transaction graph, or TDAG, generally consists of the states and the transactions as transitions between the states, together with conditions for the consistency and validity of transactions. We instantiate the TDAG model for three prominent blockchain systems: Bitcoin, Ethereum, and Hyperledger Fabric. We specify the states and transactions as well as the validity conditions of the TDAG for each one. This demonstrates the applicability of the model and formalizes the transaction-level semantics that these systems aim for.
Brandon Broadnax, Valerie Fetzer, Jörn Müller-Quade, Andy Rupp
ePrint ReportUsing these transformations, we are able to show that some of the known relations for public-key encryption do not carry over to commitments. In particular, we show that, surprisingly, parallel non-malleability and parallel CCA-security are not equivalent for commitment schemes. This stands in contrast to the situation for public-key encryption where these two notions are equivalent as shown by Bellare et al. at CRYPTO 99.
Marie-Sarah Lacharité, Kenneth G. Paterson
ePrint ReportFrederik Armknecht, Jens-Matthias Bohli, Ghassan O. Karame, Wenting Li
ePrint ReportBenedikt B\"unz, Jonathan Bootle, Dan Boneh, Andrew Poelstra, Pieter Wuille, Greg Maxwell
ePrint ReportBulletproofs greatly improve on the linear (in $n$) sized range proofs currently used to implement Confidential Transactions (CT) in Bitcoin and other cryptocurrencies. Moreover, Bulletproofs supports aggregation of range proofs, so that a party can prove that $m$ commitments lie within a given range by providing only an additive $O(\log(m))$ group elements over the length of a {\em single} proof. To aggregate proofs from multiple parties, we enable the parties to generate a single proof without revealing their inputs to each other via a simple multi-party computation (MPC) protocol for constructing Bulletproofs. This MPC protocol uses either a constant number of rounds and linear communication, or a logarithmic number of rounds and logarithmic communication.
Bulletproofs build on the techniques of Bootle et al. (EUROCRYPT 2016). Beyond range proofs, Bulletproofs provide short zero-knowledge proofs for general arithmetic circuits while only relying on the discrete logarithm assumption and without requiring a trusted setup. We discuss many applications that would benefit from Bulletproofs, primarily in the area of cryptocurrencies. The efficiency of Bulletproofs is particularly well suited for the distributed and trustless nature of blockchains.
Innsbruck, Austria, 18 June - 19 June 2018
Event CalendarSubmission deadline: 18 February 2018
Notification: 31 March 2018
University of Surrey, Guildford Surrey UK
Job Posting
The University of Surrey is recognized by the National Cyber Security Centre as one of only fourteen Academic Centres of Excellence in Cyber Security Research. Its security related research is focused on protocol analysis, security verification, trusted computing, data privacy, access control, privacy preserving security, cryptography, and distributed ledger technologies.
The position offers the platform for the research fellow to work within a group and develop skills to become an independent researcher. The successful candidate will work under the direction of Professor Steve Schneider, together with Dr Francois Dupressoir and Dr Helen Treharne. The project is also collaborative with King’s College London.
We are looking for applicants that demonstrate strong research and analytical skills, have strong communication skills and enthusiasm for developing their own research ideas. Applicants should also have skills in software engineering for web applications, and an understanding of computer security and basic cryptography. Knowledge of Distributed Ledger Technologies would be an advantage.
Applicants should have a PhD in a relevant subject or equivalent professional experience. The post is available to start by January 1st 2018, and runs in the first instance to August 2019.
Salary: £30,688 to £39,992 per annum
Closing date for applications: 23 November 2017
Contact: Professor Steve Schneider
Professor in Secure Systems
Department of Comoputer Science, Guildford, Surrey, GU2 7XH
s.schneider (at) surrey.ac.uk
More information: https://jobs.surrey.ac.uk/Vacancy.aspx?ref=034017-R
Aalborg University, Denmark
Job PostingThe position is part of the workpackage Secure Computation of the project above, and the central task consists in evaluating the applicability of the different existing results in secure multiparty computation to the algorithms used in control theory and developing new results/optimizations in this setting.
We are looking for a postdoc that has strong background on mathematics. The ideal candidate has expertise in cryptography and more specifically secure computation but candidates from associated areas are also welcome.
The project starts in January 2018 and hence we would like a candidate that starts then or shortly thereafter. The deadline for the application is 29th November and the applications needs to be done through the following webpage: http://www.stillinger.aau.dk/vis-stilling/?vacancy=939782 .
Closing date for applications: 29 November 2017
Contact: Ignacio Cascudo, Associate Professor, Department of Mathematics, Aalborg University.
Email: ignacio (at) math.aau.dk
More information: http://www.stillinger.aau.dk/vis-stilling/?vacancy=939782
University of Luxembourg
Job Posting- Design and analysis of symmetric cryptographic primitives
- Side-channel attacks on block ciphers and countermeasures
- Financial cryptography, crypto-currencies, blockchain tech
- Privacy enhancing technologies
- White-box cryptography
We offer
You will work in an exciting international environment and will have the opportunity to participate in the development of a large IT security-focused research center (>200 people researching all aspects of IT security). The University offers highly competitive salaries and is an equal opportunity employer.
Applications, written in English, should be submitted by e-mail and should include:
• Curriculum Vitae (including your contact address, photo, work experience, publications)
• A research statement indicating your interests, main achievements, motivation (max 1 page)
Closing date for applications: 15 January 2018
Contact: Prof. Alex Biryukov
More information: https://www.cryptolux.org/index.php/Home
Royal Holloway, University of London
Job PostingApplications are invited for a postdoctoral research assistant position in the Information Security Group (ISG) at Royal Holloway, University of London, to work in the area of post-quantum cryptography. The goal of this industry-funded two-year project is to investigate and propose novel methods and techniques for hardware implementation of popular and promising post-quantum cryptographic schemes.
The post is based at Royal Holloway’s main campus in Egham, Surrey, within commuting distance from London. The successful applicant will work with Prof Carlos Cid, Dr Martin Albrecht and other members of the ISG, in the research of efficient and secure hardware implementations of post-quantum cryptographic schemes. The researcher will consider the specific mathematical structure and features of these schemes, and will investigate the most suitable algorithmic and parameter choices for FPGA implementations. Moreover, potential trade-offs involving implementation costs, speed and scalability will be evaluated, considering for example the deployment in particular environments.
We are looking for a candidate with a PhD degree in a relevant subject and strong background and experience in FPGA implementation, ideally of cryptographic algorithms. The post will last for two years and the ideal candidate should be able to start should be able to start as soon as possible.
Established in 1990, the Information Security Group at Royal Holloway was one of the first dedicated academic groups in the world to conduct research and teaching in information security. The ISG is today a world-leading interdisciplinary research group with 20 full-time members of staff, 10 post-doctoral research assistants and over 50 PhD students working on a range of subjects in cyber security, in particular cryptography.
Closing date for applications: 10 December 2017
Contact: Carlos Cid (carlos.cid (at) rhul.ac.uk), Martin Albrecht (martin.albrecht (at) rhul.ac.uk)
More information: https://jobs.royalholloway.ac.uk/vacancy.aspx?ref=0817-306-R
09 November 2017
Reyhaneh Rabaninejad, Maryam Rajabzadeh Asaar, Mahmoud Ahmadian Attari, Mohammad Reza Aref
ePrint ReportSatrajit Ghosh, Tobias Nilges
ePrint ReportIn this paper, we present a new approach to compute the intersection between sets based on a primitive called Oblivious Linear Function Evaluation (OLE). On an abstract level, we use this primitive to efficiently add two polynomials in a randomized way while preserving the roots of the added polynomials. Setting the roots of the input polynomials to be the elements of the input sets, this directly yields an intersection protocol with optimal asymptotic communication complexity $O(m\kappa)$. We highlight that the protocol is information-theoretically secure assuming OLE.
We also present a natural generalization of the 2-party protocol for the fully malicious multi-party case. Our protocol does away with expensive (homomorphic) threshold encryption and zero-knowledge proofs. Instead, we use simple combinatorial techniques to ensure the security. As a result we get a UC-secure protocol with asymptotically optimal communication complexity $O((n^2+nm)\kappa)$, where $n$ is the number of parties, $m$ is the set size and $\kappa$ the security parameter. Apart from yielding an asymptotic improvement over previous works, our protocols are also conceptually simple and require only simple field arithmetic.
Along the way we develop tools that might be of independent interest.
Qingju Wang, Yonglin Hao, Yosuke Todo, Chaoyun Li, Takanori Isobe, Willi Meier
ePrint ReportWe apply our technique to stream cipher TRIVIUM and KREYVIUM. For TRIVIUM, benefited from our techniques, we, for the first time, can recover the superpoly of 833-rounds with cube dimension 73, and complexity $2^{76.91}$. Furthermore, for 833-rounds, we can find a new cube of dimension 74, with only one secret key bit involved, thus the complexity is $2^{75}$. For 839-rounds, we find a cube of dimension 78, with only one secret key bit involved in the superpoly.
For KREYVIUM, the lower complexity evaluation enables us to recover the superpoly of 849-rounds with time complexity of $2^{81.7}$. Moreover, we find a new cube of dimension 102, which can achieve 888-rounds with complexity $2^{111.38}$. So far as we know, all of our results are the best.
Tianren Liu, Vinod Vaikuntanathan, Hoeteck Wee
ePrint ReportIn this work, we *refute* two natural strengthenings of the above conjecture:
-- First, we present secret-sharing schemes for a family of $2^{2^{n/2}}$ monotone functions over $\{0,1\}^n$ with sub-exponential share size $2^{O(\sqrt{n} \log n)}$. This *unconditionally* refutes the stronger conjecture that circuit size is a lower bound on the share size.
-- Second, we disprove the analogous conjecture for non-monotone functions. Namely, we present non-monotone secret-sharing schemes for *every* access function over $\{0,1\}^n$ with shares of size $2^{O(\sqrt n \log n)}$.
Our construction draws upon a rich interplay amongst old and new problems in information-theoretic cryptography: from secret-sharing, to multi-party computation, to private information retrieval. Along the way, we also construct the first multi-party conditional disclosure of secrets (CDS) protocols for general functions $F:\{0,1\}^n \rightarrow \{0,1\}$ with communication complexity $2^{O(\sqrt n \log n)}$.
University of Lübeck, Germany
Job Posting- Side channel attacks and mitigations
- System security for IoT, mobile and Cloud systems
- Trusted computing and trusted execution environments
- Applied cryptography
- Secure microarchitectures
As ideal candidate, you are highly motivated, knowledgeable in security and willing to perform creative and deep research. You have a degree in computer science, electronics or applied mathematics. Prior experience in low-level programming, code analysis, cryptography and/or machine learning are an asset. Publications at relevant conferences such as USENIX Security, CCS, S&P, CHES, CRYPTO, EUROCRYPT are expected for PostDoc applications.
The brand-new Institute for IT Security at University of Lübeck performs research on various topics in IT security. We offer an attractive working environment as part of an international cutting-edge research team, at the shores of the Baltic sea.
Please provide a resume, transcripts, a motivational statement and contact information of at least two references.
Closing date for applications: 15 December 2017
Contact: Thomas Eisenbarth thomas.eisenbarth (at) uni-luebeck.de
More information: https://www.its.uni-luebeck.de/en/jobs.html