International Association
for Cryptologic Research

Robust property-preserving hash (PPH) functions, recently introduced by Boyle, Lavigne, and Vaikuntanathan [ITCS 2019], compress large inputs $x$ and $y$ into short digests $h(x)$ and $h(y)$ in a manner that allows for computing a predicate $P$ on $x$ and $y$ while only having access to the corresponding hash values. In contrast to locality-sensitive hash functions, a robust PPH function guarantees to correctly evaluate a predicate on $h(x)$ and $h(y)$ even if $x$ and $y$ are chosen adversarially \emph{after} seeing $h$.

Our main result is a robust PPH function for the exact hamming distance predicate \[ \mathsf{HAM}^t(x, y) = \begin{cases} 1 &\text{if } d( x, y) \geq t \\ 0 & \text{Otherwise}\\ \end{cases} \] where $d(x, y)$ is the hamming-distance between $x$ and $y$. Our PPH function compresses $n$-bit strings into $\mathcal{O}(t \lambda)$-bit digests, where $\lambda$ is the security parameter. The construction is based on the q-strong bilinear discrete logarithm assumption.

Along the way, we construct a robust PPH function for the set intersection predicate \[ \mathsf{INT}^t(X, Y) = \begin{cases} 1 &\text{if } \vert X \cap Y\vert > n - t \\ 0 & \text{Otherwise}\\ \end{cases} \] which compresses sets $X$ and $Y$ of size $n$ with elements from some arbitrary universe $U$ into $\mathcal{O}(t\lambda)$-bit long digests. This PPH function may be of independent interest. We present an almost matching lower bound of $\Omega(t \log t)$ on the digest size of any PPH function for the intersection predicate, which indicates that our compression rate is close to optimal. Finally, we also show how to extend our PPH function for the intersection predicate to more than two inputs.

The specific order of commands agreed upon when running state machine replication (SMR) is immaterial to fault-tolerance: all that is required is for all correct deterministic replicas to follow it. In the permissioned blockchains that rely on Byzantine fault tolerant (BFT) SMR, however, nodes have a stake in the specific sequence that ledger records, as well as in preventing other parties from manipulating the sequencing to their advantage. The traditional specification of SMR correctness, however, has no language to express these concerns. This paper introduces Byzantine ordered consensus, a new primitive that augments the correctness specification of BFT SMR to include specific guarantees on the total orders it produces; and a new architecture for BFT SMR that, by factoring out ordering from consensus, can enforce these guarantees and prevent Byzantine nodes from controlling ordering decisions (a Byzantine oligarchy). These contributions are instantiated in Pompe, a BFT SMR protocol that is guaranteed to order commands in a way that respects a natural extension of linearizability.

Attribute-based encryption received widespread attention as soon as it was proposed. However, due to its specific characteristics, some restrictions on attribute set in attribute-based encryption are not flexible enough in actual operation. In addition, since access authorities are determined according to users' attributes, users sharing the same attributes are difficult to be distinguished. Once a malicious user makes illicit gains by their decryption authorities, it is difficult to track down specific users. This paper follows practical demands to propose a more flexible key-policy attribute-based encryption scheme with black-box traceability. The scheme has a constant size of public parameters which can be utilized to construct attribute-related parameters flexibly, and the method of traitor tracing in broadcast encryption is introduced to achieve effective malicious user tracing. In addition, the security and feasibility can be proved by the security proofs and performance evaluation in this paper.

FIDO's Universal-2-Factor (U2F) is a web-authentication mechanism designed to provide resilience to real-time phishing—a class of attacks that undermines multi-factor authentication by allowing an attacker to relay second-factor one-time tokens from the victim user to the legitimate website in real-time. A U2F dongle is simple to use, and is designed to ensure users have complete mental models of proper usage. We show that social engineering attacks allow an adversary to downgrade FIDO’s U2F to alternative authentication mechanisms. Websites allow such alternatives to handle dongle malfunction or loss. All FIDO-supporting wesbites in Alexa's top 100 allow choosing alternatives to FIDO, and are thus vulnerable to real-time phishing attacks. We crafted a phishing website that mimics Google login’s page and implements a FIDO-downgrade attack. We then ran a carefully-designed user study to test the effect on users. We found that, while registering FIDO as their second authentication factor, 55 % of participants fell for real-time phishing, and another 35% would potentially be susceptible to the attack in practice.

There are many examples of how to assess the side-channel resistance of a hardware implementation for a given order, where one has to take into account all transitions and glitches produced by a given design. However, microprocessors do not conform with the ideal circuit model which is typically used to gain confidence in the security of masking against side-channel attacks. As a result, masked software implementations in practice do not exhibit the security one would expect in theory. In this paper, we generalize and extend work by Papagiannopoulos and Veshchikov to describe the ways in which a microprocessor may leak. We show that the sources of leakage are far more numerous than previously considered and highly dependent on the platform. We further describe how to write high-level code in the C programming language that allows one to work around common micro-architectural features. In particular, we introduce implementation techniques to reduce sensitive combinations made by the CPU and which are devised so as to be preserved through the optimizations made by the compiler. However, these techniques cannot be proven to be secure. In this paper, we seek to highlight leakage not considered in current models used in proofs and describe some potential solutions. We apply our techniques to two case studies (DES and AES) and show that they are able to provide a modest level of security on several platforms.

This paper analyzes and optimizes quantum circuits for computing discrete logarithms on binary elliptic curves, including reversible circuits for fixed-base-point scalar multiplication and the full stack of relevant subroutines. The main optimization target is the size of the quantum computer, i.e., the number of logical qubits required, as this appears to be the main obstacle to implementing Shor's polynomial-time discrete-logarithm algorithm. The secondary optimization target is the number of logical Toffoli gates.

For an elliptic curve over a field of 2^n elements, this paper reduces the number of qubits to 7n+[log_2(n)]+9. At the same time this paper reduces the number of Toffoli gates to 48n^3+8n^(log_2(3)+1)+352n^2 log_2(n)+512n^2+O(n^(log_2(3))) with double-and-add scalar multiplication, and a logarithmic factor smaller with fixed-window scalar multiplication. The number of CNOT gates is also O(n^3). Exact gate counts are given for various sizes of elliptic curves currently used for cryptography.

In this work we develop optimized software implementationsfor ForkAE, a second round candidate in the ongoing NIST lightweight cryptography standardization process. Moreover, we analyze the perfor-mance and efficiency of different ForkAE implementations on two em-bedded platforms: ARM Cortex-A9 and ARM Cortex-M0.First, we study portable ForkAE implementations. We apply a decryption optimization technique which allows us to accelerate decryption by up to 35%. Second, we go on to explore platform-specific software op-timizations. In platforms where cache-timing attacks are not a risk, we present a novel table-based approach to compute the SKINNY round function. Compared to the existing portable implementations, this technique speeds up encryption and decryption by 20% and 25%, respectively. Additionally, we propose a set of platform-specific optimizations for processors with parallel hardware extensions such as ARM NEON. Without relying on parallelism provided by long messages (cf. bit-sliced implementations), we focus on the primitive-level ForkSkinny parallelism provided by ForkAE to reduce encryption and decryption latency by up to 30%. We benchmark the performance of our implementations on the ARM Cortex-M0 and ARM Cortex-A9 processors and give a comparison withthe other SKINNY-based schemes in the NIST lightweight competition– SKINNY-AEAD and Romulus

The protection of cryptographic implementations against power analysis attacks is of critical importance for many applications in embedded systems. The typical approach of protecting against these attacks is to implement algorithmic countermeasures, like masking. However, implementing these countermeasures in a secure and correct manner is challenging. Masking schemes require the independent processing of secret shares, which is a property that is often violated by CPU microarchitectures in practice. In order to write leakage-free code, the typical approach in practice is to iteratively explore instruction sequences and to empirically verify whether there is leakage caused by the hardware for this instruction sequence or not. Clearly, this approach is neither efficient, nor does it lead to rigorous security statements.

In this paper, we overcome the current situation and present the first approach for co-design and co-verification of masked software implementations on CPUs. First, we present Coco, a tool that allows us to provide security proofs at the gate-level for the execution of a masked software implementation on a concrete CPU. Using Coco , we analyze the popular 32-bit RISC-V Ibex core, identify all design aspects that violate the security of our tested masked software implementations and perform corrections, mostly in hardware. The resulting secured Ibex core has an area overhead around 10%, the runtime of software on this core is largely unaffected, and the formal verification with Coco of an, e.g., first-order masked Keccak S-box running on the secured Ibex core takes around 156 seconds. To demonstrate the effectiveness of our suggested design modifications, we perform practical leakage assessments using an FPGA evaluation board.

Deep learning-based SCA represents a powerful option for profiling side-channel analysis. Numerous results in the last few years indicate neural networks can break targets protected with countermeasures even with a relatively small number of attack traces. Intuitively, the more powerful neural network architecture we require, the more effort we need to spend in its hyperparameter tuning. Current results commonly use random search and reach good performance. Yet, we remain with the question of how good are such architectures if compared with the architectures that are carefully designed by following a specific methodology. Unfortunately, the works considering methodologies are sparse and difficult to ease without prior knowledge about the target.

This work proposes an automated way for deep learning hyperparameter tuning that is based on Bayesian Optimization. We build a custom framework denoted as AutoSCA that supports both machine learning and side-channel metrics. Our experimental analysis shows that Bayesian optimization performs well regardless of the dataset, leakage model, or neural network type. What is more, we find a number of neural network architectures outperforming state-of-the-art attacks. Finally, we note that random search, despite being considered not particularly powerful, manages to reach top performance for a number of considered settings. We postulate this happens since the datasets are relatively easy to break, and there are many neural network architectures reaching top performance.

An oblivious RAM (ORAM), introduced by Goldreich and Ostrovsky (STOC '87 and J. ACM '96), is a technique for hiding RAM's access pattern. That is, for every input the distribution of the observed locations accessed by the machine is essentially independent of the machine's secret inputs. Recent progress culminated in a work of Asharov et al. (EUROCRYPT '20), obtaining an ORAM with (amortized) logarithmic overhead in total work, which is known to be optimal.

Oblivious Parallel RAM (OPRAM) is a natural extension of ORAM to the (more realistic) parallel setting where several processors make concurrent accesses to a shared memory. It is known that any OPRAM must incur logarithmic work overhead and for highly parallel RAMs a logarithmic depth blowup (in the balls and bins model). Despite the significant recent advances, there is still a large gap: all existing OPRAM schemes incur a poly-logarithmic overhead either in total work or in depth.

Our main result closes the aforementioned gap and provides an essentially optimal OPRAM scheme. Specifically, assuming one-way functions, we show that any Parallel RAM with memory capacity~$N$ can be obliviously simulated in space $O(N)$, incurring only $O(\log N)$ blowup in (amortized) total work as well as in depth. Our transformation supports all PRAMs in the CRCW mode and the resulting simulation is in the CRCW mode as well.

Job Description As a Principal Engineer/Cryptographer at Intel, you will lead complex, multi-disciplinary projects to advance cutting-edge applied cryptography within Intel's chips. The ideal candidate is comfortable implementing multiple types of cryptographic algorithms and able to research new constructions and guide hardware, firmware and software teams. The candidate should be experienced in cryptographic solution formulation and problem solving.

Responsibilities include the following:

• Drive a specific strategic cryptographic initiative across Intel
• Collaborate with internal stakeholders to contribute to other strategic objectives of Intel's Cryptography team
• Influence internal security policies and standards regarding cryptography and security
• Collaborate with other team members on internal research activities
• Perform cryptanalytical reviews of algorithms, protocols and implementations
• Track relevant state-of-the-art academic cryptographic research
• Guide and mentor the develop of junior engineers in the technical leadership pipeline

Qualifications
Minimum work experience requirements:
10+ years experience in cryptography/cryptographic implementation and an advanced degree in cryptography or related discipline; or 15+ years experience in cryptography/cryptographic implementation
Preferred qualifications:

• Experience with industrial security engineering, preferably significant contributions to large projects
• Knowledge of computer architecture, CPU, SoC, chipsets, BIOS, Firmware, Drivers, and other compute paradigms
• Very good understanding of side-channel attacks, including architectural and physical attacks
• Familiarity with hardware design toolsets, including RTL
• Familiarity and experience with software languages (C, C++, Java, Python, Go, etc.)
• Strong track record of contributions to the crypto community (papers in well-established conferences, patents, standards)
• Familiarity with latest developments in the area of post-quantum algorithms

For more details please see the full job posting link.Closing date for applications:

Contact: David Wheeler (david.m.wheeler@intel.com)

More information: https://jobs.intel.com/ShowJob/Id/2616826/Principal-Engineer-Senior-Cryptographer

We are looking for a PhD student and a Postdoc to work on Security of Beyond 5G networks under INSPIRE-5Gplus and 6G Flagship projects. The PhD student position is open for students with a Masters Degree in EE or CS fields. More info about Projects: INSPIRE-5Gplus: https://www.inspire-5gplus.eu/ 6G Flagship: https://www.oulu.fi/6gflagship/ If you are interested, Please Contact: madhusanka.liyanage@oulu.fi or Pawani.porambage@oulu.fi

Closing date for applications:

Contact: Madhusanka Liyanage (madhusanka.liyanage@oulu.fi)

More information: https://sites.google.com/view/madhusanka/home

Dr. Yang Zhang (https://yangzhangalmo.github.io/) at CISPA Helmholtz Center for Information Security (Germany) is looking for several fully-funded Ph.D. students working on the following topics:

• Machine learning security and privacy
• Biomedical privacy
• Misinformation detection

Requirements for Ph.D. students:

• A bachelor/master degree in Computer Science, Information Security, or Mathematics
• Excellent English (knowledge of German is not required)
• Good knowledge about machine learning/data mining
• Excellent programming skills

What we offer:

• Full-time working contract (12-month E13-level salary, ~2,400 euros per month)
• Excellent research environment
• Strong supervision

To apply, please send your:

• CV
• Transcript

to zhang@cispa.de

We also have positions for postdocs, if you are interested, please send an email with your CV to zhang@cispa.de as well.

Closing date for applications:

Contact: Yang Zhang

As part of the SecInt Doctoral College (SecInt-DK), TU Wien is offering ten positions as university assistant (Pre-Doc) for 4 years. Expected start: 01.01.2021.

Tasks:

• Collaboration on current research projects
• Deepening scientific knowledge
• Collaboration in academic teaching
• Writing a dissertation and publications
• Participation in regular events organized by the SecInt Doctoral College
• Completion of an internship with one of our international research partners
• Presentation of research results and participation in scientific event

The Research Projects: The SecInt Doctoral college offers 10 interdisciplinary research projects from the areas of Formal Methods, Security and Privacy, and Machine Learning, that are each supervised by at least two professors from the corresponding research areas. Additional details on the individual projects can be found at https://secint.visp.wien/projects.

We offer:

• Diverse and exciting tasks, with lots of interdisciplinary collaboration
• Continuing personal and professional education and flexible working hours
• Central location with very good accessibility in a city regularly ranked first worldwide for life quality
• Possibility of an internship with one of our international research partners
• Very competitive salary

Your profile:

• Completion of a master or diploma curriculum in computer science or another related field
• Experience in Mathematical Modeling, Computational Logic, Formal Methods, Security and Privacy, Robotics and/or Machine Learning
• Very good skills in English communication and writing.
• Readiness for interdisciplinary collaboration
• Team competences, problem-solving skills and innovative ability

A predoctoral researcher at TU Wien currently receives a minimum of EUR 2.196,75/month gross, 14 times/year for 30 hours/week and EUR 2.929,00/month for 40 hours/week (about EUR 28.675/year net). Relevant working experiences may increase the monthly income.

We look forward to receiving yo

Closing date for applications:

Contact: secint@visp.wien

More information: https://jobs.tuwien.ac.at/Job/136572

Several PhD positions in the domains of cryptography, computer security, privacy, and blockchain-based systems are available at the University of Connecticut (UConn), Computer Science and Engineering department, led by Prof. Ghada Almashaqbeh.

The positions provide a great opportunity for students with interest in interdisciplinary projects that combine knowledge from various fields towards the design of secure systems and protocols. We target real-world timely problems and aim to provide secure and practical solutions backed by rigorous foundations and efficient implementations/thorough performance testing. We are also interested in conceptual projects that contribute in bridging the gap between theory and practice of Cryptography. For more information about our current and previous projects please check https://ghadaalmashaqbeh.github.io/research/.

For interested students, please send your CV to ghada.almashaqbeh@uconn.edu and provide any relevant information about the topics you want to work on and the skills/related background you have.

Closing date for applications:

Contact: Ghada Almashaqbeh (ghada.almashaqbeh@uconn.edu)

More information: https://ghadaalmashaqbeh.github.io/

There are two Ph.D. positions opening at Dr. Berk Gulmezoglu's research group at the Department of Electrical and Computer Engineering of Iowa State University, Ames, IA. The research topics are side-channel attacks, ML-based analysis techniques and countermeasures. Interested students are welcomed to send their resume and unofficial transcript to bgulmez@iastate.edu Requirements: Preferred to be at the majors of Computer Science or Computer Engineering. Interested in software-based microarchitectural attacks or deep learning algorithms. Proficiency in programming languages such as C/C++, Python and Javascript. Great enthusiasm of conducting research oriented tasks. Degree: B.S. and M.S. graduates Deadline: preferably starting at Spring 2021. Fall 2021 is also okay. Positions are open until they are filled.

Closing date for applications:

Contact: Berk Gulmezoglu bgulmez@iastate.edu

More information: https://www.ece.iastate.edu/bgulmez/

Lund University was founded in 1666 and is repeatedly ranked among the world’s top 100 universities. The University has 40 000 students and more than 8 000 staff based in Lund, Helsingborg and Malmö.

The topic of the project is the study of the security of software implementations of cryptographic primitives and protocols. You will investigate attacks using side-channel leakage in software implementations, in particular libraries implementing current or future standard security protocols and cryptographic primitives such as OpenSSL. The focus can be on cache-timing attacks of different forms and will include both developing attacks as well as different protection methods, such as guaranteeing a constant-time implementation. It can also be on power analysis attacks on devices executing software and its protected implementations.

Work duties: The main duties involved in a post-doctoral position is to conduct research. Teaching may also be included, but up to no more than 20% of working hours. The position include the opportunity for three weeks of training in higher education teaching and learning.

Qualification requirements: Appointment to a post-doctoral position requires that the applicant has a PhD, or an international degree deemed equivalent to a PhD, within the subject of the position, completed no more than three years before the last date for applications. Under special circumstances, the doctoral degree can have been completed earlier.

Additional requirements: Very good oral and written proficiency in English. Publications in top conferences in the crypto and security community.

Terms of employment: This is a full-time, fixed-term employment of a maximum of 2 years with competitive salary (about 42kSEK per month before tax).

Last application date: 09.Nov.2020

Closing date for applications:

Contact: Thomas johansson (thomas@eit.lth.se)

More information: https://lu.varbi.com/en/what:job/jobID:357480/type:job/where:4/apply:1

Oblivious Transfer (OT) is a fundamental cryptographic protocol that finds a number of applications, in particular, as an essential building block for two-party and multi-party computation. We construct the first universally composable (UC) protocol for oblivious transfer secure against active static adversaries based on the Computational Diffie-Hellman (CDH) assumption. Our protocol is proven secure in the observable Global Random Oracle model. We start by constructing a protocol that realizes an OT functionality with a selective failure issue, but shown to be sufficient to instantiate efficient OT extension protocols. In terms of complexity, this protocol only requires the computation of 6 modular exponentiations and the communication of 5 group elements, five binary strings of security parameter length, and two binary strings of message length. Finally, we lift this weak construction to obtain a protocol that realizes the standard OT functionality (without any selective failures) at an additional cost of computing 9 modular exponentiations and communicating 4 group elements, four binary strings of security parameter length and two binary strings of message length. As an intermediate step before constructing our CDH based protocols, we design generic OT protocols from any OW-CPA secure public-key encryption scheme with certain properties, which could potentially be instantiated from more assumptions other than CDH.

Selfish mining (SM) attack (Eyal and Sirer, CACM ’13) endangered Proof-of-Work blockchains by allowing a rational mining pool with a hash power (&#945;) much less than 50% of the whole network to deviate from the honest mining algorithm and to steal from the fair shares of honest miners. Since then, the attack has been studied extensively in various settings, for understanding its interesting dynamics, optimizing it, and mitigating it. In this context, first, we propose generalized formulas for the calculation of revenue and profitability from SM-type attacks. Second, we propose two different SM-type attacks on the state-of-the-art mitigation algorithm “Freshness Preferred” (Heilman, FC ’14). Our Oracle mining attack works on the setting with forgeable timestamps (i.e., if timestamps are not generated by an authority) and our Bold mining attack works on the setting with both forgeable or unforgeable timestamps (i.e., even if an authority issues timestamps). Although the use of timestamps would be promising for selfish mining mitigation, the analyses of our attacks show that Freshness Preferred is quite vulnerable in the presence of rational miners, as any rational miner with &#945; >0 can directly benefit from our attacks. Third, we propose an SM mitigation algorithm Fortis with forgeable timestamps, which protects the honest miners’ shares against any attacker with &#945;<27.0% against all the known SM-type attacks.

I describe a blockchain design that hides the transaction graph from Blockchain Analyzers. The design is based on the realization that today the miner creating a block needs enough information to verify the validity of transactions, which makes details about the transactions public and thus allows blockchain analysis. Some protocols, such as Mimblewimble, obscure the transaction amounts but not the source of the funds which is enough to allow for analysis. The insight in this technical note is that the block creator can be restricted to the task of ensuring no double spends. The task of actually verifying transaction balances really belongs to the receiver. The receiver is the one motivated to verify that she is receiving a valid transaction output since she has to convince the next receiver that the balances are valid, otherwise no one will accept her spending transaction. The bulk of the transaction can thus be encrypted in such a manner that only the receiver can decrypt and examine it. Opening this transaction allows the receiver to also open previous transactions to allow her to work her way backward in a chain until she arrives at the coin generation blocks and completely verify the validity of the transaction. Since transactions are encrypted on the blockchain a blockchain analyzer cannot create a transaction graph until he is the receiver of a transaction that allows backward tracing through to some target transaction.