IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
31 March 2021
James Bartusek, Giulio Malavolta
* A witness encryption (WE) scheme for QMA.
* A publicly-verifiable non-interactive zero-knowledge (NIZK) argument for QMA.
* A two-message publicly-verifiable witness-indistinguishable (ZAPR) argument for QMA.
* An attribute-based encryption (ABE) scheme for BQP.
* A secret sharing scheme for monotone QMA.
30 March 2021
University of Lübeck, Germany
University of Lübeck is a modern and renowned research university specialized in Computer Science and Engineering, Medicine and Life Sciences.
The young and growing Institute for IT Security performs cutting-edge research in security-critical applications and their protection in insecure environments. Explored methods range from secure computation methods and cryptographic protocols to software and hardware mechanisms for protecting system security. In addition, we analyze security of existing systems as well as the improvement and automation of analysis techniques for protocols and implementations.
Your Profile:
In order to complement our team, we are looking for a full-time PhD researcher in one the following topics:
- Analysis and design of trusted execution environments and secure microarchitectures
- Secure distributed computing
- Automated code analysis and application security analysis
Required Qualifications:
As ideal candidate, you are highly motivated, independent and able to perform creative and deep research. Your main areas of interest are in system security and/or applied cryptography and you have experience in the areas of cryptography, algorithms, code analysis, embedded programming, and/or machine learning.
You have a MSc degree in Computer Science, Applied Mathematics, Information and Computer Engineering, or comparable related field and an excellent command of written and spoken English.
We offer excellent working conditions in an international team of cutting-edge researchers and ample opportunity to collaborate with renowned researchers worldwide.
Closing date for applications:
Contact: Thomas Eisenbarth: its.bewerbungen@uni-luebeck.de
Please apply by April 15 and mention position code 1011/21.
More information: https://www.its.uni-luebeck.de/en/jobs.html
Fabian Boemer, Sejun Kim, Gelila Seifu, Fillipe D.M. de Souza, Vinodh Gopal
Javad Doliskani
Hao Chen
Shlomi Dolev, Matan Liber
Florian Breuer, Vipul Goyal, Giulio Malavolta
In this work, we develop new cryptographic techniques to integrate security policies (developed in the traditional banking domain) in the blockchain settings. We propose a system where a smart contract is given the custody of the user's funds and has the ability to invoke a two-factor authentication (2FA) procedure in case of an exceptional event (e.g., a particularly large transaction or a key recovery request). To enable this, the owner of the account secret-shares the answers of some security questions among a committee of users. When the 2FA mechanism is triggered, the committee members can provide the smart contract with enough information to check whether an attempt was successful, and nothing more.
We then design a protocol that securely and efficiently implements such a functionality: The protocol is round-optimal, is robust to the corruption of a subset of committee members, supports low-entropy secrets, and is concretely efficient. As a stepping stone towards the design of this protocol, we introduce a new threshold homomorphic encryption scheme for linear predicates from bilinear maps, which might be of independent interest.
To substantiate the practicality of our approach, we implement the above protocol as a smart contract in Ethereum and show that it can be used today as an additional safeguard for suspicious transactions, at minimal added cost. We also implement a second scheme where the smart contract additionally requests a signature from a physical hardware token, whose verification key is registered upfront by the owner of the funds. We show how to integrate the widely used universal two-factor authentication (U2F) tokens in blockchain environments, thus enabling the deployment of our system with available hardware.
Marc Schoolderman, Jonathan Moerman, Sjaak Smetsers, Marko van Eekelen
We have formally verified such code: a library which implements elliptic curve cryptography on 8-bit AVR microcontrollers. The chosen implementation is the most efficient currently known for this microarchitecture. It consists of over 3000 lines of assembly instructions. Building on earlier work, we use the Why3 platform to model the code and prove verification conditions, using automated provers. We expect the approach to be re-usable and adaptable, and it allows for validation. Furthermore, an error in the original implementation was found and corrected, at the same time reducing its memory footprint. This shows that practical verification of cutting-edge code is not only possible, but can in fact add to its efficiencyand is clearly necessary.
Sook Yan Hue, Jason Chia, Ji Jian Chin
Yi Liu, Qi Wang, Siu-Ming Yiu
In this paper, we propose the \emph{first desirable} mechanism that is practical and supports a wide variety of computing tasks --- evaluation of arbitrary functions that can be represented as polynomials. We introduce a new cryptographic notion called \emph{blind polynomial evaluation} and instantiate it with an explicit protocol. We further combine this notion with the blockchain paradigm to provide a \emph{practical} framework that can satisfy the requirements mentioned above.
Prabhanjan Ananth, Fatih Kaleoglu
In this work, we study uncloneable encryption schemes, where the encryption key can be re-used to encrypt multiple messages. We present two constructions from minimal cryptographic assumptions: (i) a private-key uncloneable encryption scheme assuming post-quantum one-way functions and, (ii) a public-key uncloneable encryption scheme assuming a post-quantum public-key encryption scheme.
Onur Gunlu, Peter Trifonov, Muah Kim, Rafael F. Schaefer, Vladimir Sidorenko
29 March 2021
Robert Bosch GmbH, Corporate Research; Stuttgart, Germany
The Robert Bosch GmbH is looking forward to your application!
Job Description
- As a PhD in our research group you are contributing to research and development projects in an open source context.
- This includes understanding, evaluating and applying Privacy-Preserving Computing Technologies (PPCTs) including Computing On Encrypted Data techniques, Trusted Execution Environments, and methods for Statistical Disclosure Control.
- Embedded into a team of security and cloud technology experts, you apply your knowledge on PPCTs to design, implement and evaluate PPCT-based solutions in the context of the Franco-German BMBF/MESRI-funded CRYPTECS research project.
- Thanks to your insights, you help combine PPCTs and Cloud Native technologies to make PPCTs ready for use in an industrial context.
- Your responsibility includes the design, development and prototypical implementation of PPCT solutions. You push the state of the art in the field of PPCTs and publish your results together with renowned researchers from the international CRYPTECS consortium.
Qualifications
- Education: Very good master’s degree in computer science or related discipline, ideally combined with initial experience in the area of Cloud Native technologies
- Personality: Positive team player, who is highly motivated, has an innovative mindset, is eager to learn new things, and is passionate about applied research
- Working Practice: Initial hands-on experience with software development, ideally in an open source context
- Experience and Knowledge: Knowledge in the area of cryptography, ideally experience in PPCTs and modern Cloud Native technologies
- Languages: Fluent in English (written and spoken) <
Closing date for applications:
Contact:
Need support during your application?
Kevin Heiner (Human Resources), Phone: +49 711 811 12223
Need further information about the job?
Dr. Sven Trieflinger (Functional Department), Phone: +49 711 811 24801
More information: https://smrtr.io/5fm_3
27 March 2021
Shlomi Dolev, Stav Doolman
Markulf Kohlweiss, Varun Madathil, Kartik Nayak, Alessandra Scafuro
In this work we show that this intuition is flawed. Even ideal anonymous broadcast channels do not suffice to protect the identity of the stakeholder who proposes a block.
We make the following contributions. First, we show a formal network-attack against Ouroboros Crypsinous, where the adversary can leverage network delays to distinguish who is the stakeholder that added a block on the blockchain. Second, we abstract the above attack and show that whenever the adversary has control over the network delay -- within the synchrony bound -- loss of anonymity is inherent for any protocol that provides liveness guarantees. We do so, by first proving that it is impossible to devise a (deterministic) state-machine replication protocol that achieves basic liveness guarantees and better than $(1-2\f)$ anonymity at the same time (where $\f$ is the fraction of corrupted parties). We then connect this result to the PoS setting by presenting the tagging and reverse tagging attack that allows an adversary, across several executions of the PoS protocol, to learn the stake of a target node, by simply delaying messages for the target. We demonstrate that our assumption on the delaying power of the adversary is realistic by describing how our attack could be mounted over the Zcash blockchain network (even when Tor is used). We conclude by suggesting approaches that can mitigate such attacks.
Christian Majenz, Christian Schaffner, Mehrdad Tahmasbi
André Schrottenloher
This problem has become ubiquitous in cryptanalytic algorithms. Applications include variants in which the XOR operation is replaced by a modular addition (k-SUM) or other non-commutative operations (e.g., the composition of permutations). The case where a single solution exists on average is of special importance.
The generic study of quantum algorithms k-XOR (and variants) was started by Grassi et al. (ASIACRYPT 2018), in the case where many solutions exist. At EUROCRYPT 2020, Naya-Plasencia and Schrottenloher defined a class of "quantum merging algorithms" obtained by combining quantum search. They represented these algorithms by a set of "merging trees" and obtained the best ones through linear optimization of their parameters.
In this paper, we give a new, simplified representation of merging trees that makes their analysis easier. As a consequence, we improve the quantum time complexity of the Single-solution k-XOR problem by relaxing one of the previous constraints, and making use of quantum walks. Our algorithms subsume or improve over all previous quantum generic algorithms for Single-solution k-XOR. For example, we give an algorithm for 4-XOR (or 4-SUM) in quantum time $\widetilde{\mathcal{O}}(2^{7n/24})$.
Jiaxin Guan, Mark Zhandry
We first propose the notion of online obfuscation, capturing the goal of disappearing programs in the bounded storage model. We give a negative result for VBB security in this model, but propose candidate constructions for a weaker security goal, namely VGB security. We then demonstrate the utility of VGB online obfuscation, showing that it can be used to generate disappearing ciphertexts and signatures. All of our applications are NOT possible in the standard model of cryptography, regardless of computational assumptions used.