## IACR News

Here you can see all recent updates to the IACR webpage. These updates are also available:

#### 28 November 2022

###### Kaveh Aasaraai, Emanuele Cesena, Rahul Maganti, Nicolas Stalder, Javier Varela, Kevin Bowers

ePrint Report###### Dan Boneh, Aditi Partap, Lior Rotem

ePrint Report###### Srinivasan Raghuraman, Yibin Yang

ePrint Report###### Daniele Friolo, Matteo Salvino, Daniele Venturi

ePrint ReportFollowing Fischlin (ICALP 2005), we study the complete non-malleability of KEMs obtained via the FO transform. Intuitively, a KEM is completely non-malleable if no adversary can maul a given public key and ciphertext into a new public key and ciphertext encapsulating a related key for the underlying blockcipher.

On the negative side, we find that KEMs derived via FO are not completely non-malleable in general. On the positive side, we show that complete non-malleability holds in the ROM by assuming the underlying PKE scheme meets an additional property, or by a slight tweak of the transformation.

###### Alexandre Debant, Lucca Hirschi

ePrint Report###### Yann Disser, Daniel Günther, Thomas Schneider, Maximilian Stillger, Arthur Wigandt, Hossein Yalame

ePrint ReportIn this work, we study UCs that simulate circuits consisting of ($\rho \rightarrow \omega$)-Lookup Tables (LUTs) that map $\rho$ inputs to $\omega$ outputs. Existing UC constructions can be easily extend to ($\rho \rightarrow$ 1)-LUTs (we call this the fixed UC construction). We further extend this to ($\rho \rightarrow \omega$)-LUTs. Unfortunately, the size of the fixed UC construction is linear in the largest input size $\rho$ of the LUT, i.e., even if only a single LUT in the circuit has a large input size, the size of the whole UC is dominated by this LUT size. To circumvent this, we design a \emph{dynamic} UC construction, where the dimensions of the individual LUTs are public. We implement the fixed and dynamic UC constructions based on the UC construction by Liu et al., which also is the first implementation of their construction. We show that the concrete size of our dynamic UC construction improves by at least $2\times$ over Liu et al.'s UC for all benchmark circuits, that are representative for many PFE applications.

###### Seunghwan Park, Chi-Gon Jung, Aesun Park, Joongeun Choi, Honggoo Kang

ePrint Report###### Philipp Hoenisch, Subhra Mazumdar, Pedro Moreno-Sanchez, Sushmita Ruj

ePrint Report###### Shah Fahd

ePrint Report###### Moumita Dutta, Chaya Ganesh, Sikhar Patranabis, Nitin Singh

ePrint ReportOur compiler incurs significantly lower computational costs and competitive communication overheads when compared to the best existing solutions, while entirely avoiding the (potentially expensive) protocol-specific techniques and pre-processing requirements that are inherent to these solutions. For $n$-party MPC protocols with abort security where each party has $\ell$ inputs, our compiler incurs $O(n\log \ell)$ communication overall and a computational overhead of $O(\ell)$ group exponentiations per party (the corresponding overheads for the most efficient existing solution are $O(n^2)$ and $O(\ell n)$). Finally, for a corruption threshold $t

Along the way, we make several technical contributions that are of independent interest. This includes the notion of distributed proofs of knowledge and concrete realizations of the same for several relations of interest, such as proving knowledge of many popularly used digital signature schemes, and proving knowledge of opening of a Pedersen commitment. We also illustrate the practicality of our approach by extending the well-known MP-SPDZ library with our compiler, thus yielding prototype authenticated MPC protocols.

###### Trey Li

ePrint Report###### Matt Davison, Ken King, Trevor Miller

ePrint Report###### Carlos Aguilar-Melchor, Nicolas Gama, James Howe, Andreas Hülsing, David Joseph, Dongze Yue

ePrint ReportAt the heart of our proposal is a new approach to amplify the soundness of any MPC protocol that uses additive secret sharing. An MPCitH protocol with $N$ parties can be repeated $D$ times using parallel composition to reach the same soundness as a protocol run with $N^D$ parties. However, the former comes with $D$ times higher communication costs, often mainly contributed by the usage of $D$ `auxiliary' states (which in general have a significantly bigger impact on size than random states). Instead of that, we begin by generating $N^D$ shares, arranged into a $D$-dimensional hypercube of side $N$ containing only one `auxiliary' state. We derive from this hypercube $D$ sharings of size $N$ which are used to run $D$ instances of an $N$ party MPC protocol. This approach leads to an MPCitH protocol with $1/N^D$ soundness error, requiring $N^D$ offline computation, only $ND$ online computation, and only $1$ `auxiliary'. As the, potentially offline, share generation phase is generally inexpensive, this leads to trade-offs that are superior to just using parallel composition.

Our novel method of share generation and aggregation not only improves certain MPCitH protocols in general but also shows in concrete improvements of signature schemes. Specifically, we apply it to the work of Feneuil, Joux, and Rivain (CRYPTO'22) on code-based signatures, and obtain a new signature scheme that achieves a 3.3x improvement in global runtime, and a 15x improvement in online runtime for their shortest signatures size (8.5 kB). It is also possible to leverage the fact that most computations are offline to define parameter sets leading to smaller signatures: 6.7 kB for 60 ms offline, or 5.6 kB for 700 ms offline. For NIST security level 1, online signature cost is around 3 million cycles (1 ms on commodity processors), regardless of signature size.

###### Matvei Kotov, Alexander Treier, Ivan Buchinskiy

ePrint Report###### James Bartusek, Sanjam Garg, Abhishek Jain, Guru-Vamsi Policharla

ePrint ReportIn this work, we address the privacy vs. content moderation question through the lens of pre-constrained cryptography [Ananth et al., ITCS 2022]. We introduce the notion of set pre-constrained (SPC) group signatures that guarantees security against malicious key generators. SPC group signatures offer the ability to trace users in messaging systems who originate pre-defined illegal content (such as child sexual abuse material), while providing security against malicious service providers.

We construct concretely efficient protocols for SPC group signatures, and demonstrate the real-world feasibility of our approach via an implementation. The starting point for our solution is the recently introduced Apple PSI system, which we significantly modify to improve security and expand functionality.

###### Technology Innovation Institute (TII) - Abu Dhabi, UAE

Job PostingTechnology Innovation Institute (TII) is a recently-established publicly-funded research institute in Abu Dhabi (UAE). It is home to a diverse community of leading scientists and engineers from across the globe.

Job DescriptionWe are looking for permanent researchers to join the Cryptographic Protocols team within the Cryptography Research Center (CRC) at TII. The main aim of the team is to conduct applied academic research in areas relating to cryptographic protocols, such as: TLS, QUIC, Tor, Key Exchange, Secure Channels, Cryptographic Primitives, Privacy Enhancing Technologies, MLS and Secure Messaging, and Probabilistic Data Structures in Adversarial Environments. The nature of the research spans both theory and practice, covering aspects such as provable security, security models, efficient designs, implementation aspects, and attacks.

Applicants should have completed (or be close to completing) their PhD in a related area, and postdoctoral research experience will be valued. Preference will be given to applicants with publications in top-tier venues such as CRYPTO, EUROCRYPT, ASIACRYPT, ACM CCS, IEEE S&P, and USENIX.

Required Skills:- Fluency in English (verbal and written) and an ability to communicate research effectively.
- Good problem-solving skills and an ability to conduct research independently.
- Good interpersonal and collaborative skills.
- Solid knowledge in cryptography.

- Research experience in Key Exchange, Signatures, Onion Routing, Privacy-Enhancing Technologies, and Zero Knowledge.
- Programming, Software Engineering, experience in implementing cryptographic primitives and attacks on real-world cryptosystems, reverse engineering of closed-source protocols.

- Vibrant working environment, flexible working conditions, and travel funding.
- Industry-competitive tax-free salary.
- Family-wide health insurance and children’s education allowance.
- Sunshine all year round.

**Closing date for applications:**

**Contact:** Jean Paul Degabriele
(jeanpaul.degabriele@tii.ae).

#### 27 November 2022

###### Royal Holloway, University of London

Job PostingThe Centre for Doctoral Training (CDT) at Royal Holloway, University of London seeks to recruit PhD students to work in the area of cryptography. Examples for potential topics include:

- Foundations of Witness Encryption and Smart Encryption (supervised by Saqib Kakvi)
- Secure Coded Caching (supervised by Siaw-Lynn Ng)
- Applications of Time and Delay in Cryptographic Protocols (supervised by Elizabeth Quaglia)
- Privacy-Preserving Applications based on Secure Multi-Party Computation (supervised by Christian Weinert)

The crypto team at Royal Holloway, as part of the Information Security Group (ISG), has a strong track record in cryptographic research, including algorithm design and analysis, post-quantum cryptography, homomorphic encryption, and applications of secure computation.

Applicants are expected to have a background in mathematics, computer science, or a related discipline. Prospective applicants are welcome to contact CDT administrator Claire Hudson (CyberSecurityCDT@rhul.ac.uk) or any member of staff they might be interested to work with. For more information about the crypto team, please visit our website [2].

The CDT can offer approximately ten studentships per year, three of which can be awarded to international students (including EU and EEA). Please ensure you are familiar with the eligibility criteria set by UKRI and their terms and conditions. In order to apply, please visit the CDT website [3] and follow the application instructions. The studentship includes a (tax-free) maintenance of £23,668.00 for each academic year.

[1] https://www.findaphd.com/phds/information-security-group/?c0MPwk50

[2] https://cryptography.isg.rhul.ac.uk

[3] https://www.royalholloway.ac.uk/cdt

**Closing date for applications:**

**Contact:** CyberSecurityCDT@rhul.ac.uk

###### Eötvös Loránd University

Job Posting- CV
- Motivation Letter
- Two recommendation letters (these should be sent by the recommending person directly to the above e-mail address)

Please send your applications by 31st January 2023.

**Closing date for applications:**

**Contact:** Péter Kutas (kuppabt@inf.elte.hu)

###### Department of Computer Science, School of Engineering, Universidad Catolica de Chile

Job Posting**Closing date for applications:**

**Contact:** Marcelo Arenas, marenas@ing.puc.cl

**More information:** https://www.ing.uc.cl/trabaja-con-nosotros/areas-to-apply-2/

###### Department of Computer Science, University of Luxembourg

Job Posting
A postdoctoral position is available in the APSIA research group (led by Prof. Peter Y. A. Ryan) in the Department of computer Science at the University of Luxembourg. The successful candidate is expected to do research in line with ‘’quantum safe proofs’’ (QSP) project funded by Luxembourg National Research Fund.
The successful candidate will conduct the QSP project in collaboration with Prof. Peter Y. A. Ryan, Prof. Anne Broadbent (University of Ottawa, Canada) and Dr. Ehsan Ebrahimi (PI, University of Luxemburg).

The duration of the position is two years. The yearly gross salary for every Postdoctoral researcher at the UL is around EUR 77167 (full time) . The starting date would be as early as 02.01.2023 (Feb 2023).

The successful candidate will conduct the following tasks:

- Research on post-quantum security of proof systems and its impact to applications like cryptocurrencies and electronic voting systems.
- Research on Quantum Proof Systems: for instance, complexity classes QMA, QIP, etc.
- Participate in teaching tasks and Ph.D. and M.Sc. students supervisions
- Collaboration with writing progress reports

- A Ph.D. degree in Computer Science, Mathematics or Physics with the focus on Cryptography and its intersection with Quantum Computation & Information.
- Experience working on quantum-secure proof systems or quantum proof systems is a plus
- Competitive research record in cryptography or quantum computation & information
- Strong mathematical CS background
- Fluent written and verbal communication skills in English are required

**Closing date for applications:**

**Contact:** Ehsan Ebrahimi, ehsan.ebrahimi@uni.lu