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04 March 2021
Pedro Hecht
CryptoLux Group, University of Luxembourg
The CryptoLux group of the University of Luxembourg has a vacancy for a post-doctoral researcher in the area of symmetric cryptography. The successful candidate will contribute to a research project entitled Analysis and Protection of Lightweight Cryptographic Algorithms (APLICA), which is funded by the Luxembourgish Fonds National de la Recherche and the German Research Foundation. Starting in 2021, APLICA will run over a period of 3 years as a joint research project between the CryptoLux group and the Workgroup for Symmetric Cryptography of Ruhr-University Bochum. The mission of the APLICA project is to develop new cryptanalytic techniques for lightweight authenticated encryption algorithms and hash functions, and to design and implement new countermeasures against side-channel attacks that are suitable for constrained devices.
Candidates must have a Ph.D. degree in symmetric cryptography or a closely related field. Preference will be given to candidates with a strong publication record that includes at least one paper at an IACR conference/workshop or one of the top-4 security conferences. Experience in software development for embedded systems or mounting side-channel attacks is a plus. Candidates with an interest to conduct research in one of the following areas are particularly encouraged to apply:
- Cryptanalysis of authenticated encryption algorithms or hash functions
- Leakage resilience or leakage reduction by design (e.g. modes of operation)
- Security evaluation of leakage-resilient primitives or constructions
The position is available from Jan. 2021 on basis of a fixed-term contract for 3 years. The University of Luxembourg offers excellent working conditions and a highly competitive salary. Interested candidates are invited to send their application by email to Alex Biryukov before Apr. 1, 2021 (early submission is strongly encouraged, applications will be processed upon receipt). The application material should contain a cover letter explaining the candidate's research interests, a CV (incl. photo), a list of publications, scans of diploma certificates, and contact details of 3 references.
Closing date for applications:
Contact: Prof. Alex Biryukov (alex.biryukov@uni.lu)
More information: https://www.fnr.lu/projects/analysis-and-protection-of-lightweight-cryptographic-algorithms/
Fujitsu Laboratories of America
This is a remote position; we are accepting applications from exceptional graduate students based in USA, UK or Japan. The selected candidate will closely work with researchers based in Sunnyvale, California. We offer attractive remuneration and typical length of internship is 12 weeks. Start date is flexible.
Closing date for applications:
Contact: Avradip Mandal (amandal at fujitsu dot com)
More information: https://www.fujitsu.com/us/about/businesspolicy/tech/rd/research/computer-security/cryptography-and-privacy/
IMDEA Software Institute, Madrid, Spain
The IMDEA Software Institute offers a postdoc position in the area of security and privacy in blockchain. The work may involve a combination of (i) identification of security threats and privacy leakages in cryptocurrencies (e.g., hardware wallets, layer-2 scalability solutions, cross-chain protocols, cybercrime operations), (ii) design and evaluation of cryptographic protocols to enhance the security, privacy, scalability and interoperability of current cryptocurrencies. The postdoc will work under the supervision of Pedro Moreno-Sánchez and Juan Caballero.
Who should apply?Applicants should have a PhD in computer science or a related discipline with an excellent track-record and an interest in privacy-enhancing technologies, applied cryptography, and data analysis. Good command of English both spoken and written is required.
Working at IMDEA SoftwareThe position is based in Madrid, Spain where the IMDEA Software Institute is situated. Salaries are internationally competitive and include attractive conditions such as access to an excellent public healthcare system. The working language at the institute is English. Knowledge of Spanish is not required.
DatesThe position is for 2 years. The preferred starting date is June 2021 with some flexibility.
How to apply?Applicants interested in the position should submit their application at https://careers.software.imdea.org/ using reference code 2021-03-postdoc-spblockchain. Review of applications will begin immediately and close when the position is filled or on April 2nd, 2021.
Closing date for applications:
Contact: pedro.moreno(at)imdea.org and/or juan.caballero(at)imdea.org
More information: https://software.imdea.org/open_positions/2021-03-postdoc-spblockchain.html
03 March 2021
Pramod Bhatotia, Markulf Kohlweiss, Lorenzo Martinico, Yiannis Tselekounis
We show that under an attested execution setup $\Gatt$ we can realise cryptographic functionalities that are unrealizable in the standard model. We propose a new primitive of Functional Encryption for Stateful and Randomised functionalities (FESR) and an associated protocol, Steel, that realizes it. We show that Steel UC-realises FESR in the universal composition with global subroutines model (TCC 2020). Our work is also a validation of the compositionality of earlier work (Iron}, CCS 2017) capturing (non-stateful) hardware-based functional encryption.
As the existing functionality for attested execution of Pass et al. (Eurocrypt 2017) is too strong for real world use, we propose a weaker functionality that allows the adversary to conduct rollback and forking attacks. We show that the stateful variant of $\Steel$, contrary to the stateless variant corresponding to Iron, is not secure in this setting and propose several mitigation techniques.
Daniel Slamanig, Christoph Striecks
In this work, we resolve these issues and present the first UE constructions with uni- and even no-directional key updates. We show that such UE schemes can be constructed in the standard model via the notion of dual system groups from the standard d-Lin assumption in prime-order bilinear groups. Our approach of constructing UE significantly departs from previous ones and in particular views UE from the perspective of puncturable encryption (Green and Miers, S&P 2015). Towards constructing UE, as an stepping stone, we introduce a variant of puncturable encryption that additionally support puncturing of ciphertexts. This turns out to be a useful abstraction on our way to construct UE and may be of independent interest.
Christoph Dobraunig, Lorenzo Grassi, Anna Guinet, Daniël Kuijsters
In this paper, we present Ciminion, an encryption scheme minimizing the number of field multiplications in large binary or prime fields, while using a very lightweight linear layer. In contrast to other schemes that aim to minimize field multiplications in GF(2^n) or GF(p), Ciminion relies on the Toffoli gate to improve the non-linear diffusion of the overall design. In addition, we have tailored the primitive for the use in a Farfalle-like construction in order to minimize the number of rounds of the used primitive, and hence, the number of field multiplications as far as possible.
Peter Rindal, Phillipp Schoppmann
Katharina Boudgoust, Corentin Jeudy, Adeline Roux-Langlois, Weiqiang Wen
Bernardo David, Lorenzo Gentile, Mohsen Pourpouneh
Katharina Boudgoust, Adeline Roux-Langlois
Claudio Orlandi, Peter Scholl, Sophia Yakoubov
- Homomorphic secret sharing. We construct homomorphic secret sharing for branching programs with *negligible* correctness error and supporting *exponentially large* plaintexts, with security based on the decisional composite residuosity (DCR) assumption.
- Correlated pseudorandomness. Pseudorandom correlation functions (PCFs), recently introduced by Boyle et al. (FOCS 2020), allow two parties to obtain a practically unbounded quantity of correlated randomness, given a pair of short, correlated keys. We construct PCFs for the oblivious transfer (OT) and vector oblivious linear evaluation (VOLE) correlations, based on the quadratic residuosity (QR) or DCR assumptions, respectively. We also construct a pseudorandom correlation generator (for producing a bounded number of samples, all at once) for general degree-2 correlations including OLE, based on a combination of (DCR or QR) and the learning parity with noise assumptions.
- Public-key silent OT/VOLE. We upgrade our PCF constructions to have a *public-key setup*, where after independently posting a public key, each party can locally derive its PCF key. This allows completely *silent generation* of an arbitrary amount of OTs or VOLEs, without any interaction beyond a PKI, based on QR, DCR, a CRS and a random oracle. The public-key setup is based on a novel non-interactive vector OLE protocol, which can be seen as a variant of the Bellare-Micali oblivious transfer protocol.
Ben Marshall, Dan Page, James Webb
Yuval Ishai, Russell W. F. Lai, Giulio Malavolta
In this work, we propose a simple compiler for HSS evaluating multivariate polynomials based on two building blocks: (1) homomorphic encryption for linear functions or low-degree polynomials, and (2) information-theoretic HSS for low-degree polynomials. Our compiler leverages the power of the first building block towards improving the parameters of the second.
We use our compiler to generalize and improve on the HSS scheme of Lai, Malavolta, and Schröder [ASIACRYPT'18], which is only efficient when the number of servers is at most logarithmic in the security parameter. In contrast, we obtain efficient schemes for polynomials of higher degrees and an arbitrary number of servers. This application of our general compiler extends techniques that were developed in the context of information-theoretic private information retrieval (Woodruff and Yekhanin [CCC'05]), which use partial derivatives and Hermite interpolation to support the computation of polynomials of higher degrees.
In addition to the above, we propose a new application of HSS to MPC with preprocessing. By pushing the computation of some HSS servers to a preprocessing phase, we obtain communication-efficient MPC protocols for low-degree polynomials that use fewer parties than previous protocols based on the same assumptions. The online communication of these protocols is linear in the input size, independently of the description size of the polynomial.
Jesús-Javier Chi-Domínguez, Krijn Reijnders
Jean-Sebastien Coron, Lorenzo Spignoli
Shoichi Kamada
In Crypto 2000, Okamoto, Tanaka and Uchiyama introduced the concept of quantum public key cryptosystems and proposed a knapsack cryptosystem, so-called OTU cryptosystem. However, no known algorithm breaks the OTU cryptosystem.
In this paper, we introduced Szemer\'{e}di-type assumptions, which are the imitations of the statement of Szemer\'{e}di's theorem on arithmetic progressions. From this mathematical point of view, we make clear what the average case and the worst case are. For low density attacks, we give better heuristics for orthogonal lattices than Gaussian heuristics. Consequently, we show that the OTU scheme can be broken under some heuristic assumptions.
Ghada Almashaqbeh, Fabrice Benhamouda, Seungwook Han, Daniel Jaroslawicz, Tal Malkin, Alex Nicita, Tal Rabin, Abhishek Shah, Eran Tromer
We present a new MPC model which avoids this privacy leak. To achieve this, we utilize a blockchain in a novel way, incorporating smart contracts and arbitrary parties that can be incentivized to perform computation (bounty hunters, akin to miners). Security is maintained under a monetary assumption about the parties: an honest party can temporarily supply a recoverable collateral of value higher than the computational cost an adversary can expend.
We thus construct non-interactive MPC protocols with strong security guarantees (full security, no residual leakage) in the short term. Over time, as the adversary can invest more and more computational resources, the security guarantee decays. Thus, our model, which we call Gage MPC, is suitable for secure computation with limited-time secrecy, such as auctions.
A key ingredient in our protocols is a primitive we call Gage Time Capsules (GaTC): a time capsule that allows a party to commit to a value that others are able to reveal but only at a designated computational cost. A GaTC allows a party to commit to a value together with a monetary collateral. If the original party properly opens the GaTC, it can recover the collateral. Otherwise, the collateral is used to incentivize bounty hunters to open the GaTC. This primitive is used to ensure completion of Gage MPC protocols on the desired inputs.
As a requisite tool (of independent interest), we present a generalization of garbled circuit that are more robust: they can tolerate exposure of extra input labels. This is in contrast to Yaos garbled circuits, whose secrecy breaks down if even a single extra label is exposed.
Finally, we present a proof-of-concept implementation of a special case of our construction, yielding an auction functionality over an Ethereum-like blockchain.