## IACR News

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#### 03 July 2020

###### KU Leuven, Belgium
Job Posting
This position in the COSIC research group of the KU Leuven, addresses valorization opportunities in new forms of cryptography that support calculations on encrypted data, without having to decrypt the data. These new forms of cryptography include fully homomorphic encryption, multi-party computation, trusted execution environments and related topics.

The Innovation Manager will identify opportunities for bilateral projects and research platforms, technology transfer, and potentially spin-off companies, including the definition of licenses, patents or other forms of valorization. All these tasks are executed in coordination with KU Leuven Research and Development. In particular, the Innovation Manager will assist in defining and maintaining a strategic research agenda to create a continuum between fundamental research, strategic research and applied research.

The lndustrial Research Fund (lOF) of KU Leuven forms a bridge between strategic basic research, technological innovations and industrial collaborations. Based on cooperations with KU Leuven research groups and different stakeholders from industry and society, we aim to broaden our valorization portfolio and to increase the transfer of knowledge. We have a team of more than 40 experienced innovation managers involved in the development of practical and innovative technological solutions based on the expertise and infrastructure of the research groups within KU Leuven.

Profile

• PhD or equivalent research expertise in applied cryptography
• Preferably industrial experience
• At least a high level understanding or parts of MPC, FHE, PQC, TEE
• Experience in valorization of research results
• Creative, enthusiastic, with a strong commitment to research valorization
• Proactive, entrepreneurial mindset
• Strong communication skills, including international and intercultural
• Willing to travel globally
Offer An exciting and challenging job, focused on continuous innovation and development in a transdisciplinary and international context. We offer a permanent position as Innovation Manager of the Industrial Research Fund (IOF) at KU

Closing date for applications:

Contact: Nigel Smart (nigel.smart@kuleuven.be) Ingrid Verbauwhede (ingrid.verbauwhede@kuleuven.be) Frederik Vercauteren (frederik.vercauteren@kuleuven.be)

#### 01 July 2020

###### London, United Kingdom, 30 November - 1 December 2020
Event Calendar
Event date: 30 November to 1 December 2020
###### Aizuwakamatsu, Japan, 30 January - 2 February 2020
Event Calendar
Event date: 30 January to 2 February 2020

#### 30 June 2020

###### Fujitsu Laboratories of America
Job Posting
The Security and Cryptography team in Fujitsu Laboratories of America is looking for an engineer for contributing to opensource blockchain projects. You will work closely with a team of cryptographers and security researchers located in Sunnyvale, California and Tokyo, Japan. Your main task will be secure software development in C/C++/Rust/golang/Nodejs as part of Fujitsu Laboratory's OSS activity in Hyperledger. In addition, you will also be encouraged to write academic papers based on your work leading to publications in top tier cryptography and security conferences.

Profile Description:

• Proven experience in production quality software development.
• Previous experience and code contributions to open source projects is a plus.
• Experience in implementation of cryptographic libraries.
• Graduate level knowledge of crypto theory. Familiarity with threshold cryptosystems and multiparty protocols (MPC). Academic publications in Crypto/Security is a plus.
• Experience in design and implementation of large software systems and writing secure code in C/C++/Rust/Golang.
• Familiarity with blockchain systems such as Hyperledger Fabric and/or Ethereum.
• Ability to meet deliverables and deadlines with minimal supervision.
• Fluent in written and spoken english.
Working hours are flexible. Initially you will be offered a full time (we are also open to offering part time) remote contractor position for six months. Depending on your performance and status of the project, the contract can be extended or can be converted to a full time permanent position based on Sunnyvale, California.

Deadline for Application: Open until the position is filled.
Start Date: Immediate, but flexible.
Salary: Very attractive, depends on experience.

Closing date for applications:

###### Max Planck Institute for Security and Privacy
Job Posting

The Max Planck Institute (MPI) for Security and Privacy is looking for motivated students to apply for a Ph.D. program. The research will be conducted on the theory of cryptography and computer security and more specifically in one of the following topics:

• Homomorphic encryption and code obfuscation
• Zero-knowledge proofs and succinct arguments
• Cryptocurrencies and blockchains
• Post-quantum and lattice-based cryptography
• Multi-party computation
• Other research proposals by the candidate will also be considered, depending on the common interests.

The ideal candidate shall satisfy the following requirements:

• Have a Master degree or equivalent (or is close to complete one) in computer science, mathematics, or related fields
• Is fluent in English and has excellent communication and writing skills
• Is familiar with probability theory and mathematical proofs. Strong background in cryptography, linear algebra, number theory, or complexity theory is a plus
• Most importantly, is passionate about learning new concepts and determined to solve challenging questions in the theory of cryptography and computer security
• Publications (or manuscripts under submission) in related areas are greatly valued but are not mandatory

The MPI for Security and Privacy is co-located with the Ruhr University of Bochum (Germany) and offers a vibrant atmosphere for research that spans across all aspects of computer security. The Ph.D. program is entirely in English and the knowledge of German is not required for a successful career at MPI.

The position is fully funded (100%) and paid according to the E-13 pay category. The starting date if flexible but ideally somewhere in fall 2020. To apply for the position, send an email to Giulio Malavolta (address below) including the following documents:

• A curriculum vitae
• 2-3 recommendation letters from previous advisors or employers
• A brief cover letter (half page at most) describing your research interests

If you have any question, don’t hesitate to get in touch.

Closing date for applications:

Contact: Giulio Malavolta (giulio.malavolta@berkeley.edu)

• ###### Huawei Technologies Duesseldorf Gmbh (Munich Research Center, Germany)
Job Posting

• Identifying weaknesses in existing 3GPP radio access network technologies including 4G and 5G (NR). • Develop and promote proposals to mitigate the security/privacy issues identified. • Cooperate with universities and other eco-system partners on security research and analysis • Help shape the industry with new innovation via standardization bodies e.g. 3GPP, ETSI, etc. • Engage with customers and regulators in order to help shape a secure ICT world. • Work with the world leading researchers across the world on the most advanced technologies including AI, IoT under the scope of 5G. • Help steer our 5G products and solutions security. • Provide analysis and insight of industry trends. • Generate product security roadmap recommendations.

Our requirements:

• PhD in computer science or advanced PhD with focus on telecommunication security (preferably radio access technologies, the 3GPP air-interface protocol stack). • Several years of experience in network security research, specifically in the domains of protocol analysis, vulnerability detection, protocol correctness, protocol verification, etc. • Several years of experience researching and developing tools/demos/PoCs which demonstrate the impact of such security issues (vulnerabilities) on the network. • Several years of experience researching and implementing mitigation solutions (PoC/Demo level) for protocol vulnerabilities including algorithms development, performance/cost and impact analysis of algorithms implementation. • Openness to work in a diversified work environment with unique work cultures. • Experience in presenting technical information to both technical and non-technical audience. • Fluent in English (written and spoken).

Must be eligible to work in the EU to be considered for this position.

By applying to this position, you agree with our PRIVACY STATEMENT. You can read in full our privacy policy via the link below.

https://career.huawei.com/reccampportal/portal5/grcprivacy.html

For further information on the requirements please click on the link below:

https://apply.worka

Closing date for applications:

Contact: Viet-Duc Benedikt Lai duc.lai.ext@huawei.com

###### Indian Institute of Technology Delhi (Workplace: IIT Bhilai, Raipur)
Job Posting
Work Sub-area:
• Lightweight Cryptography including authentication protocols
• Secure boot mechanisms for embedded/IoT devices

Funding Agency: Ministry of Communication and Information Technology

Tentative Duration: Upto:31/03/2021

Qualifications: B. Tech. (with GATE qualification) / MSc. (with NET/SET qualification) / M.C.A. (with GATE* qualification) 1st class or equivalent in the appropriate discipline.

Desirables: Basic knowledge of cryptography or some experience with using RFID tags or experience on some Raspberry based project or using Trusted Platform Modules (TPMs)

Note: The requirement of qualifying NET/SET/GATE qualification may be relaxed by the Committee in case of highly meritorious candidates.

Closing date for applications:

Contact:
Dr. Dhiman Saha,
Department of Electrical Engineering and Computer Science,
Indian Institute of Technology Bhilai.
email: dhiman [at] iitbhilai [dot] ac [dot] in

• ###### Lior Rotem, Gil Segev
ePrint Report
Despite the fundamental importance of delay functions, repeated squaring in RSA groups (Rivest, Shamir and Wagner '96) is the only candidate offering both a useful structure and a realistic level of practicality. Somewhat unsatisfyingly, its sequentiality is provided directly by assumption (i.e., the function is assumed to be a delay function).

We prove sharp thresholds on the sequentiality of all generic-ring delay functions relative to an RSA modulus based on the hardness of factoring in the standard model. In particular, we show that generically speeding-up repeated squaring (even with a preprocessing stage and any polynomial number parallel processors) is equivalent to factoring.

More generally, based on the (essential) hardness of factoring, we prove that any generic-ring function is in fact a delay function, admitting a sharp sequentiality threshold that is determined by our notion of sequentiality depth. Moreover, we show that generic-ring functions admit not only sharp sequentiality thresholds, but also sharp pseudorandomness thresholds.
###### Mikhail Volkhov, Markulf Kohlweiss
ePrint Report
Due to its simplicity, succinctness, and performance, Groth16 is currently the most widely deployed succinct (zero-knowledge) argument of knowledge (SNARK) system. Groth16 is known to be perfectly zero-knowledge and knowledge sound in the generic (and algebraic) group model. However, the existing security arguments for Groth16 are silent about the soundness of the proof system in the presence of simulated proofs --- a common requirement for both the composable security and game-hopping style security analysis of protocols built using such argument systems. This important gap let to a line of work on simulation-extractable, also called simulation knowledge sound, succinct proof systems. Groth16 itself cannot satisfy the strongest notion of simulation-extractability that implies proof non-malleability --- in fact, proofs are perfectly randomizable. Surprisingly, in this short note we show that Groth16 does satisfy a weaker notion of simulation-extractability implying statement non-malleability. This property is often sufficient for typical applications that motivate the use of strong simulation-extractability. Notably, one can obtain UC security using efficient compilers.
###### Shuyang Tang
ePrint Report
A novel Nakamoto-like consensus was proposed by Tang et al. (ACISP 2019) to speed up the convergence (block finality) rate by determining a weight of a block in the blockchain by a tunable potential function of the block hash. However, the convergence of the scheme was evaluated only in an experimental way and a sudden utilization of another blockchain was not clearly explained. This article asymptotically analyses the convergence of Nakamoto-like consensus of Tang et al. by proposing a general framework for formalizing consensus schemes comprising both the classical Nakamoto consensus (bitcoin consensus) and the consensus of Tang et al. The framework contains two categories of schemes, namely, small-step consensus like the bitcoin consensus and giant-step consensus of Tang et al. Furthermore, the essence of the second chain, the even-trigger, is shown to be a necessity of realizing giant-step consensus.
###### Michael Klooß
ePrint Report
We revisit the definition of efficient algorithms and argue, that the standard runtime classes, strict probabilistic polynomial time (PPT) and expected probabilistic polynomial time (EPT) are “unnatural” from a cryptographic perspective. They are not closed under indistinguishability. Applied to EPT, this suggests computationally expected polynomial time (CEPT), the class of runtimes which are (computationally) indistinguishable from EPT. We analyse the behaviour of CEPT for zero-knowledge proofs and designated adversaries in the setting of uniform complexity (following Goldreich (JC’93)). A designated adversary is (only) efficient in the protocol it is designed to attack. This security notion, first proposed in Feige’s thesis [Fei90], is very natural, but there are obstructions to achieving it. Prior work on handling (designated) EPT adversaries by Katz and Lindell (TCC’05) requires superpolynomial hardness assumptions, whereas the work of Goldreich (TCC’07) requires “nice” adversarial behaviour under rewinding. We provide easy-to-check criteria for zero-knowledge protocols with black-box simulation in the plain model, which show that many (all known?) such protocols handle designated CEPT adversaries in CEPT.
###### Michel Abdalla
ePrint Report
In this report, we analyze the security of the trust establishment protocol used in the Olvid messaging protocol. The latter relies on the PV-SAS-MCA message cross-authentication protocol by Pasini an Vaudenay based on short authenticated strings (SAS). In order to make the implementation portable across different platforms, Olvid proposed particular instantiations of the underlying primitives used in PV-SAS-MCA in addition to some other minor modifications. Here, we show that these changes have no impact on the security of the scheme. More precisely, we formally prove that the trust establishment protocol used in Olvid is a secure message cross-authentication protocol. The proof of security is in the random-oracle model and relies on the security of the underlying pseudorandom generator. It also assumes users know each other and have an authentic channel between them.
###### Brett Hemenway Falk, Rafail Ostrovsky
ePrint Report
Data-oblivious algorithms are a key component of many secure computation protocols.

In this work, we show that advances in secure multiparty shuffling algorithms can be used to increase the efficiency of several key cryptographic tools.

The key observation is that many secure computation protocols rely heavily on secure shuffles. The best data-oblivious shuffling algorithms require $O(n \log n)$, operations, but in the two-party or multiparty setting, secure shuffling can be achieved with only $O(n)$ communication.

Leveraging the efficiency of secure multiparty shuffling, we give novel algorithms that improve the efficiency of securely sorting sparse lists, secure stable compaction, and securely merging two sorted lists.

Securely sorting private lists is a key component of many larger secure computation protocols. The best data-oblivious sorting algorithms for sorting a list of $n$ elements require $O(n \log n)$ comparisons. Using black-box access to a linear-communication secure shuffle, we give a secure algorithm for sorting a list of length $n$ with $t \ll n$ nonzero elements with communication $O(t \log^2 n + n)$, which beats the best oblivious algorithms when the number of nonzero elements, $t$, satisfies $t < n/\log^2 n$.

Secure compaction is the problem of removing dummy elements from a list, and is essentially equivalent to sorting on 1-bit keys. The best oblivious compaction algorithms run in $O(n)$-time, but they are unstable, i.e., the order of the remaining elements is not preserved. Using black-box access to a linear-communication secure shuffle, we give a stable compaction algorithm with only $O(n)$ communication.

Our main result is a novel secure merge protocol. The best previous algorithms for securely merging two sorted lists into a sorted whole required $O(n \log n)$ secure operations. Using black-box access to an $O(n)$-communication secure shuffle, we give the first secure merge algorithm that requires only $O(n \log \log n)$ communication. Our algorithm takes as input $n$ secret-shared values, and outputs a secret-sharing of the sorted list.

All our algorithms are generic, i.e., they can be implemented using generic secure computations techniques and make black-box access to a secure shuffle.

Our techniques extend naturally to the multiparty situation (with a constant number of parties) as well as to handle malicious adversaries without changing the asymptotic efficiency.

These algorithm have applications to securely computing database joins and order statistics on private data as well as multiparty Oblivious RAM protocols.
###### Daxin Huang, Qingqing Gan, Xiaoming Wang, Chengpeng Huang, Yijian Lin
ePrint Report
As a popular paradigm, crowd-sensing network emerges to achieve sensory data collection and task allocation to mobile users. On one hand these sensory data could be private and sensitive, and on the other hand, data transmission separately could incur heavy communication overhead. Fortunately, the technique of homomorphic encryption (HE) allows the addictive and/or multiplicative operations over the encrypted data as well as privacy protection. Therefore, several data aggregation schemes based on HE are proposed for crowd-sensing network. However, most of the existing schemes do not support ciphertext comparison efficiently, thus data center cannot process ciphertexts with flexibility. To address this challenge, we propose a comparable homomorphic encryption (CompHE) scheme based on Lagrange’s interpolation theorem, which enables ciphertext comparison between multiple users in crowdsensing network. Based on the Partial Discrete Logarithm and Decisional Diffie-Hellman assumption, the proposed CompHE scheme is provably secure in the random oracle model. Performance analysis confirms that the proposed scheme have improved the computational efficiency compared with existing schemes.
###### Furkan Turan, Ingrid Verbauwhede
ePrint Report
FPGAs offer many-fold acceleration to various application domains, and have become a part of cloud-based computation. However, their cloud-use introduce Cloud Service Provider (CSP) as trusted parties, who can access the hardware designs in plaintext. Therefore, the intellectual property of hardware designers is not protected against a dishonest cloud. In this paper, we propose a scheme for the confidentiality of accelerators on cloud, without limiting CSP to maintain their resources freely. Our proposed scheme is based on Proxy Re-Encryption which allows the developers to upload their accelerators to the CSPs under encryption. The CSPs cannot decrypt them; however, alter the encryption that allows the target FPGAs they pick to decrypt. In addition, our scheme allows metering the use of accelerators.
ePrint Report
Low energy consumption is an important factor in today's technologies as many devices run on a battery and there are new applications which require long runtimes with very small batteries. As many of these devices are connected to some kind of network, they require encryption/decryption to securely transmit data. Hence, the energy consumption of the cipher is an important factor for the battery life. We evaluate the energy consumption of lightweight ciphers implemented on a custom 65nm ASIC. Since the energies to measure are very small, we first introduce, compare and evaluate two techniques to precisely measure the energy consumption of a real cryptographic core. In our comparative investigations, using the PRINCE block cipher we examine the effect of the design architecture (round-based versus unrolled) on the amount of energy consumption. In addition to considering other effects (like fixed key versus random key), we compare round-based implementations of different block ciphers (PRINCE, MIDORI and SKINNY) under similar settings providing first such practical investigations.
###### Weiqiong Cao, Hongsong Shi, Hua Chen, Wei Xi, Haoyuan Li, Limin Fan, Wenling Wu
ePrint Report
Deterministic ECC-based signatures including deterministic ECDSA and EdDSA are becoming popular to be applied to blockchain and Internet of Things. Their security has received a considerable attention, and there have existed some differential fault attacks against them. However, the attacks have some problems such as high computational complexity and strict requirement of fault injection. In this paper eight efficient lattice-based fault attacks(and one differential fault attack) against deterministic ECDSA and two ones against EdDSA are proposed. All the fault models of such attacks are the random storage faults of intermediate values during signature, by which some faulty and one correct signatures are obtained to construct the models of lattice attacks(or the equations with two unknown) and thereby recover the private key.

Unlike the previous differential fault attacks based on storage faults, our attacks do not need to guess the number and location of the faulty bits, and are still effective while the previous attacks are computationally infeasible. Moreover, compared with the previous lattice-based fault attacks against the non-deterministic signatures with random nonces, our attacks have more fault models besides the faulty nonce k, and only need random fault injection. We demonstrate the effectiveness of the attacks by simulations, which shows our attacks pose real threats to deterministic signature. The upper bound of the number of the faulty bits is just slightly less than the key length. We also discuss the corresponding countermeasures against our attacks.
###### Mostafizar Rahman, Goutam Paul
ePrint Report
Recently, in Asiacrypt 2019, Bonnetain et. al have shown attacks by quantum adversaries on FX construction and Even-Mansour Cipher without using superposition queries to the encryption oracle. In this work, we use a similar approach to mount new attacks on HCTR and HCH construction. In addition, we mount attacks on HCTR, Tweakable-HCTR and HCH using the superposition queries to the encryption oracle using strategies proposed by Leander and May in Asiacrypt 2017 and Kaplan et. al in Crypto 2016.

#### 27 June 2020

###### Ward Beullens
ePrint Report
Recently, a new code based signature scheme, called LESS, was proposed with three concrete instantiations, each aiming to provide 128 bits of classical security. Two instantiations (LESS-I and LESS-II) are based on the conjectured hardness of the linear code equivalence problem, while a third instantiation, LESS-III, is based on the conjectured hardness of the permutation code equivalence problem for weakly self-dual codes. We give an improved algorithm for solving both these problems over sufficiently large finite fields. Our implementation breaks LESS-I and LESS-III in approximately 45 seconds and 2 seconds respectively on a laptop. Since the field size for LESS-II is relatively small $(\mathbb{F}_7)$ our algorithm does not improve on existing methods. Nonetheless, we estimate that LESS-II can be broken with approximately $2^{44}$ row operations.
###### Mihir Bellare, Wei Dai, Phillip Rogaway
ePrint Report
Aiming to strengthen classical secret-sharing to make it a more directly useful primitive for human end-users, we develop definitions, theorems, and efficient constructions for what we call "adept" secret-sharing. Our primary concerns are the properties we call "privacy", "authenticity", and "error correction". Privacy strengthens the classical requirement by ensuring maximal confidentiality even if the dealer does not employ fresh, uniformly random coins with each sharing. That might happen either intentionally--to enable reproducible secret-sharing--or unintentionally, when an entropy source fails. Authenticity is a shareholder's guarantee that a secret recovered using his or her share will coincide with the value the dealer committed to at the time the secret was shared. Error correction is the guarantee that recovery of a secret will succeed, also identifying the valid shares, exactly when there is a unique explanation as to which shares implicate what secret. These concerns arise organically from a desire to create general-purpose libraries and apps for secret sharing that can withstand both strong adversaries and routine operational errors.