International Association
for Cryptologic Research

With increasing autonomous features of vehicles, key issues of robotic- and automotive engineering converge toward each other. Closing existing security gaps of device communication networks will be an enabling feature for connecting autonomously interacting systems in a more secure way. We introduce a novel approach for deriving a secret key using a lightweight cipher in the firmware of a low-end control unit. In this approach, we propose to use a non-standardized lightweight algorithm with unique hardware based parameters to prevent duplicate key generation. The randomness of the selected cipher was assessed by applying the NIST statistical test suite to produced key values. By evaluating the method on a typical low-end automotive platform, we could demonstrate the realistic applicability of the solution. The proposed method counteracts a known security issue in device communication between control units not only present in automotive solutions but also in the robotics domain. The security of the implemented solution has been compared to current automotive guidelines and recommendations for the security of resource constrained devices, also present in robotics. This approach allows low-end communication systems to be enhanced by message- and device authentication.

Sampling from discrete Gaussian distribution has applications in lattice-based post-quantum cryptography. Several efficient solutions have been proposed in recent years. However, making a Gaussian sampler secure against timing attacks turned out to be a challenging research problem. In this work, we observed an important property of the input random bit strings that generate samples in Knuth-Yao sampling. We delineate a generic step-by-step method to instantiate a discrete Gaussian sampler of arbitrary standard deviation and precision by efficiently minimizing the Boolean expressions by exploiting this prop- erty. Discrete Gaussian samplers generated in this method can be up to 37% faster than the state of the art method. Finally, we show that the signing algorithm of post-quantum signature scheme Falcon using our constant-time sampler is at most 33% slower than the fastest non-constant time sampler.

This paper introduces streamlined constant-time variants of Euclid's algorithm, both for polynomial inputs and for integer inputs. As concrete applications, this paper saves time in (1) modular inversion for Curve25519, which was previously believed to be handled much more efficiently by Fermat's method, and (2) key generation for the ntruhrss701 and sntrup4591761 lattice-based cryptosystems.

Financial exchanges are typically built out of two trusted components: a trade matching and a trade settlement system. With the advent of decentralized ledgers, that perform transactions without a trusted intermediary, so called decentralized exchanges (DEX) emerged. Some DEXs propose to off-load trade order matching to a centralized system outside the blockchain to scale, but settle each trade trustlessly as an expensive on-chain transaction. While DEX are non-custodial, their order books remains trusted, a malicious exchange operator or miner could front-run trades --- i.e. alter trade order execution for financial gain. The scalability limitations of the settlement layer (e.g. Proof of Work (PoW) blockchains) moreover hinders the practical growth of such DEX architectures.

We propose TEX, a front-running resilient, non-custodial centralized exchange. Our matching system enforces the trade order sequence provided by traders, i.e. is resilient against trade sequence alteration by the exchange operator. As such the matching system can operate in conjunction with a blockchain based settlement layer (as proposed in the following), or make custodian exchanges provably accountable for their matching process. Our layer-two settlement system executes a trade without holding the assets, and allows to reach similar scales as traditional exchanges (trading volume in USD, number of trades/second), despite a slow underlying ledger. TEX might become a point of availability-failure, but we show how the settlement system's security properties would not compromise the trader's assets, even if the centralized operator is compromised and/or colludes with all other traders. We provide an evaluation on a PoW blockchain.

We introduce KL-hardness, a new notion of hardness for search problems which on the one hand is satisfied by all one-way functions and on the other hand implies both next-block pseudoentropy and inaccessible-entropy, two forms of computational entropy used in recent constructions of pseudorandom generators and statistically hiding commitment schemes, respectively. Thus, KL-hardness unifies the latter two notions of computational entropy and sheds light on the apparent "duality" between them. Additionally, it yields a more modular and illuminating proof that one-way functions imply next-block inaccessible entropy, similar in structure to the proof that one-way functions imply next-block pseudoentropy (Vadhan and Zheng, STOC '12).

Cryptocurrencies have provided a promising infrastructure for pseudonymous online payments. However, low throughput has significantly hindered the scalability and usability of cryptocurrency systems for increasing numbers of users and transactions. Another obstacle to achieving scalability is the requirement for every node to duplicate the communication, storage, and state representation of the entire network.

In this paper, we introduce the Asynchronous Consensus Zones, which scales blockchain system linearly without compromising decentralization or security. We achieve this by running multiple independent and parallel instances of single-chain consensus systems termed as zones. The consensus happens independently within each zone with minimized communication, which partitions the workload of the entire network and ensures a moderate burden for each individual node as the network grows. We propose eventual atomicity to ensure transaction atomicity across zones, which achieves the efficient completion of transactions without the overhead of a two-phase commit protocol. Additionally, we propose Chu-ko-nu mining to ensure the effective mining power in each zone to be at the same level of the entire network, making an attack on any individual zone as hard as that on the full network. Our experimental results show the effectiveness of our work: on a testbed including 1,200 virtual machines worldwide to support 48,000 nodes, our system delivers 1,000x throughput and 2,000x capacity over the Bitcoin and Ethereum networks.

The Fiat-Shamir transformation is a useful approach to building non-interactive arguments (of knowledge) in the random oracle model. Unfortunately, existing proof techniques are incapable of proving the security of Fiat-Shamir in the quantum setting. The problem stems from (1) the difficulty of quantum rewinding, and (2) the inability of current techniques to adaptively program random oracles in the quantum setting.

In this work, we show how to overcome the limitations above in many settings. In particular, we give mild conditions under which Fiat-Shamir is secure in the quantum setting. As an application, we show that existing lattice signatures based on Fiat-Shamir are secure without any modifications.

Multi-signatures allow a group of signers to jointly sign a message in a compact and efficiently verifiable signature, ideally independent of the number of signers in the group. We present the first provably secure forward-secure multi-signature scheme by deriving a forward-secure signature scheme from the hierarchical identity-based encryption of Boneh, Boyen, and Goh (Eurocrypt 2005) and showing how the signatures in that scheme can be securely composed. Multi-signatures in our scheme contain just two group elements (one from each of the base groups) and require one exponentation and three pairing computations to verify.

We propose a modular security treatment of blind signatures derived from linear identification schemes in the random oracle model. To this end, we present a general framework that captures several well known schemes from the literature and allows to prove their security. Our modular security reduction introduces a new security notion for identification schemes called One-More-Man In the Middle Security which we show equivalent to the classical One-More-Unforgeability notion for blind signatures. We also propose a generalized version of the Forking Lemma due to Bellare and Neven (CCS 2006) and show how it can be used to greatly improve the understandability of the classical security proofs for blind signatures schemes by Pointcheval and Stern (Journal of Cryptology 2000).

Cube attack is an important cryptanalytic technique against symmetric cryptosystems, especially for stream ciphers. The key step in cube attack is recovering superpoly. However, when cube size is large, the large time complexity of recovering the exact algebraic normal form (ANF) of superpoly confines cube attack. At CRYPTO 2017, Todo et al. applied conventional bit-based division property (CBDP) into cube attack which could exploit large cube sizes. However, CBDP based cube attacks cannot ensure that the superpoly of a cube is non-constant. Hence the key recovery attack may be just a distinguisher. Moreover, CBDP based cube attacks can only recover partial ANF coefficients of superpoly. The time complexity of recovering the reminding ANF coefficients is very large, because it has to query the encryption oracle and sum over the cube set. To overcome these limits, in this paper, we propose a practical method to recover the ANF coefficients of superpoly. This new method is developed based on bit-based division property using three subsets (BDPT) proposed by Todo at FSE 2016. We apply this new method to reduced-round Trivium. To be specific, the time complexity of recovering the superpoly of 832-round Trivium at CRYPTO 2017 is reduced from $2^{77}$ to practical, and the time complexity of recovering the superpoly of 839-round Trivium at CRYPTO 2018 is reduced from $2^{79}$ to practical. Then, we propose a theoretical attack which can recover the superpoly of Trivium up to 842 round. As far as we know, this is the first time that the superpoly can be recovered for Trivium up to 842 rounds.

Concrete security proofs give upper bounds on the attacker's advantage as a function of its time/query complexity. Cryptanalysis suggests however that other resource limitations - most notably, the attacker's memory - could make the achievable advantage smaller, and thus these proven bounds too pessimistic. Yet, handling memory limitations has eluded existing security proofs.

This paper initiates the study of time-memory trade-offs for basic symmetric cryptography. We show that schemes like counter-mode encryption, which are affected by the Birthday Bound, become more secure (in terms of time complexity) as the attacker's memory is reduced.

One key step of this work is a generalization of the Switching Lemma: For adversaries with $S$ bits of memory issuing $q$ distinct queries, we prove an $n$-to-$n$ bit random function indistinguishable from a permutation as long as $S \times q \ll 2^n$. This result assumes a combinatorial conjecture, which we discuss, and implies right away trade-offs for deterministic, stateful versions of CTR and OFB encryption.

We also show an unconditional time-memory trade-off for the security of randomized CTR based on a secure PRF. Via the aforementioned conjecture, we extend the result to assuming a PRP instead, assuming only one-block messages are encrypted.

Our results solely rely on standard PRF/PRP security of an underlying block cipher. We frame the core of our proofs within a general framework of indistinguishability for streaming algorithms which may be of independent interest.

Event date: 24 August 2019
Submission deadline: 25 May 2019

Event date: 26 July to 28 July 2019
Submission deadline: 15 April 2019
Notification: 23 May 2019

Event date: 17 May to 18 May 2019
Submission deadline: 18 March 2019
Notification: 25 March 2019

Kanazawa University, Japan, invites applications for an associate professor position or a tenure-track assistant professor position in advanced research area of information security, such as IT Security and Cryptography.

An appointee is expected on duty on July 1st, 2019 or at an early possible time after that.

Research budget:: In case of tenure-track assistant professor, Kanazawa University plans to provide a start-up research fund of approximately 800,000 JPY in the first year in addition to faculty research expense.

Closing date for applications: 15 March 2019

Contact: Masahiro Mambo (Contact information can be found below.)

More information: https://www.se.kanazawa-u.ac.jp/en/researchers/pdf/20190315_ec_tt_en.pdf

Simula UiB has up to four three-year PhD positions available in the field of cryptography. The following specific topics are of particular interest:

- algorithmic and theoretical aspects of side-channel security

- cryptographic protocols for privacy-preserving applications

- privacy-preserving pairing-based and lattice-based protocols for applications like blockchain

The PhD students will enter the PhD program of the Department of informatics at the University of Bergen. Applications must be submitted via https://www.simula.no/about/job/call-phd-students-cryptography-simula-uib

Closing date for applications: 30 April 2019

Contact: For questions and inquiries, please contact

Martijn Stam, email: martijn (at) simula.no

or

Helger Lipmaa, email: helger.lipmaa (at) gmail.com

More information: https://www.simula.no/about/job/call-phd-students-cryptography-simula-uib

Two Postdoc positions are available in the Information Security Group at Royal Holloway, University of London, UK.

The postdoc will work alongside Martin Albrecht and other cryptographic researchers in the ISG on topics in lattice-based cryptography and related fields. One post is funded by a joint grant between Royal Holloway and Imperial College (Cong Ling) for bridging the gap between lattice-based cryptography and coding theory (starting date: 15 April or later). The second post is funded by an EPSRC grant on investigating the security of lattice-based and post-quantum cryptographic constructions (starting date: 1 June or later). Applicants with a strong background in all areas of cryptography are encouraged to apply.

Applicants should have already completed, or be close to completing, a PhD in a relevant discipline. Applicants should have an outstanding research track record in cryptography. Applicants should be able to demonstrate scientific creativity, research independence, and the ability to communicate their ideas effectively in written and verbal form.

The ISG is one of the largest departments dedicated to information security in the world with 21 core academic staff in the department, as well as research and support staff. We work with many research partners in other departments and have circa 90 PhD students working on a wide range of security research, many of whom are fully funded through our Centre for Doctoral Training in Cyber Security. We have a strong, vibrant, embedded and successful multi-disciplinary research profile spanning from cryptography to systems security and social aspects of security. This vibrant environment incorporates visiting researchers, weekly research seminars, weekly reading groups, PhD seminars and mini conferences, the WISDOM group (Women in the Security Domain Or Mathematics) and we are proud of our collegial atmosphere and approach.

Closing date for applications: 5 April 2019

Contact: Martin Albrecht, martin.albrecht _AT_ royalholloway.ac.uk

More information: https://jobs.royalholloway.ac.uk/vacancy.aspx?ref=0219-081

The IMDEA Software Institute (Madrid, Spain) invites applications for a research internship in the area of Cryptography. The successful candidate will join the cryptography group led by Prof. Dario Fiore to work on a project within the area of zero-knowledge proofs and their applications to blockchain protocols.

Who should apply: Applicants should be MSc or PhD students in computer science, mathematics or a related discipline. Strong knowledge of cryptography and solid programming skills are required. Familiarity with cryptographic protocols, cryptography implementation libraries or C++ will be considered as a plus.

Working at IMDEA Software: The position is based in Madrid, Spain, where the IMDEA Software Institute is situated. The institute provides for travel expenses and an internationally competitive stipend. The working language at the institute is English.

Dates: The internship duration is intended to be for 4-6 months (with some flexibility). The ideal starting period is from May 2019.

How to apply: Applicants interested in the position should submit their application at https://careers.imdea.org/software/ using reference code 2019-02-intern-crypto. Deadline for applications is April 15, 2019. Review of applications will begin immediately.

Closing date for applications: 15 April 2019

Contact: For enquiries about the position, please contact:

Dario Fiore, dario.fiore (at) imdea.org

Matteo Campanelli, matteo.campanelli (at) imdea.org

More information: https://software.imdea.org/open_positions/2019-02-intern-crypto.html

This position is available immediately in Professor Mosca’s Research group. You will be working with a team of researchers and developers from academia and industry on the Open Quantum Safe project (openquantumsafe.org). You will help integrate new post-quantum cryptographic algorithms into the libOQS open-source library, and design and implement techniques for evaluating and benchmarking these cryptographic algorithms in a variety of contexts. You will be required to participate in weekly sprint meetings and perform software development tasks assigned by the project team lead, ensuring that all code contributions developed by self or integrated from 3rd party contribution sources adhere to a cohesive design and framework. The field of post-quantum cryptography is rapidly evolving, and you will need to track ongoing changes to algorithms due to peer review and advances by researchers via the the NIST Post-Quantum Cryptography project forum. Any significant findings relating to a particular PQ algorithm’s effectiveness or efficiency should be brought to the attention of team lead, and may be disclosed to other researchers in forum. In addition to algorithm research, tasks cover all aspects of the software development lifecycle and include design, programming cryptographic algorithms, integrating other cryptographic implementations into the libOQS framework, integrating libOQS into 3rd party opensource projects, testing, benchmarking and documentation. You may be required to take an ownership role in coordinating the development of a sub-component of the Open Quantum Safe project.

https://uwaterloo.ca/institute-for-quantum-computing/positions/open-quantum-safe-liboqs-cryptographic-research-architect

Closing date for applications: 30 August 2019

Contact: Michele Mosca: michele.mosca (at) uwaterloo.ca

Douglas Stebila: dstebila (at) uwaterloo.ca

More information: https://uwaterloo.ca/institute-for-quantum-computing/positions/open-quantum-safe-liboqs-cryptographic-research-architect

This post offers an exciting opportunity for an appointment to strengthen the research of our existing research, for example at the interface between security and machine learning and in data science.

The Department has a large secure systems research group, led by Professor Steve Schneider, with expertise in security by design, cryptography, authentication, verification, distributed ledger technologies, trusted systems, IoT security, program analysis and cloud security. Professor Yaochu Jin also leads a research group specialising in machine learning, complex systems and networks, Bayesian learning, neuroscience, evolutionary computation and applications of machine learning.

Closing date for applications: 17 March 2019

Contact: Helen Treharne

More information: https://jobs.surrey.ac.uk/vacancy.aspx?ref=010019