IACR News
Here you can see all recent updates to the IACR webpage. These updates are also available:
15 November 2022
Vipul Goyal, Chen-Da Liu-Zhang, Justin Raizes, João Ribeiro
ePrint ReportMotivated by real-world networks, the seminal work of Ben-Or, Canetti and Goldreich (STOC'93) initiated the study of multi-party computation for classical circuits over asynchronous networks, where the network delay can be arbitrary. In this work, we begin the study of asynchronous multi-party quantum computation (AMPQC) protocols, where the circuit to compute is quantum.
Our results completely characterize the optimal achievable corruption threshold: we present an $n$-party AMPQC protocol secure up to $t
Rasheed Kibria, Farimah Farahmandi, Mark Tehranipoor
ePrint ReportFoteini Baldimtsi, Konstantinos Chalkias, Panagiotis Chatzigiannis, Mahimna Kelkar
ePrint ReportInterestingly, mining can result in record-size cryptographic outputs, and we show that 5%-12% shorter hash digests and signatures are practically feasible even with commodity hardware. Obviously, the first thing that comes to mind is compressing addresses and transaction signatures in order to pay less gas fees in blockchain applications, but in fact even traditional TLS certificates and public keys, which are computed once and reused in every new connection, can be slightly compressed with this "mining" trick without compromising security. The effects of "compressing once - then reuse'' at mass scale can be economically profitable in the long run for both the Web2 and Web3 ecosystems. Our paradigm relies on a brute-force search operation in order to craft the primitive's output such that it fits into fewer bytes, while the "missing" fixed bytes are implied by the system parameters and omitted from the actual communication. While such compression requires computational effort depending on the level of compression, this cost is only paid at the source (typically in blockchains consisting of a single party) which is rewarded by lowered transaction fees, and the benefits of the compression are enjoyed by the whole ecosystem. As a starting point, we show how our paradigm applies to some basic primitives (commonly used in blockchain applications), and show how security is preserved using a bit security framework. Surprisingly, we also identified cases where wise mining strategies require proportionally less effort than naive brute-forcing, an example is WOTS (and inherently SPHINCS) post-quantum signatures where the target goal is to remove or compress the Winternitz checksum part. Moreover, we evaluate our approach for several primitives based on different levels of compression which concretely demonstrates the benefits (both in terms of financial cost and storage) if adopted by the community. Finally, as this work is inspired by the recent unfortunate buggy "gas golfing'' software in Ethereum, where weakly implemented functions incorrectly generated addresses (hashes) with "prefixed zeroes for gas optimization'', resulting in millions of losses, we expect our Truncator approach to be naturally applied in the blockchain space as a secure solution to more succinct transactions, addresses and states.
14 November 2022
Daniel J. Bernstein
ePrint ReportThis paper quantifies the asymptotic impact of multiple ciphertexts per public key upon existing heuristic analyses of known lattice attacks. The qualitative conclusions are that typical lattice PKEs asymptotically degrade in heuristic multi-ciphertext IND-CPA security as the number of ciphertexts increases. These PKE attacks also imply multi-ciphertext IND-CCA2 attacks against typical constructions of lattice KEMs. This shows a contradiction between (1) the existing heuristics and (2) the idea that multi-target security matches single-target security.
The asymptotic heuristic security degradation is exponential in Θ(n) for decrypting many ciphertexts, cutting a constant fraction out of the total number of bits of security, and exponential in Θ(n/log n) for decrypting one out of many ciphertexts, for conservative cryptosystem parameters. Furthermore, whether or not the existing heuristics are correct, (1) there are flaws in the claim of provable multi-target security based on MLWE, and (2) there is a 2^88-guess attack breaking one out of 2^40 ciphertexts for a FrodoKEM-640 public key.
Qianqian Yang, Ling Song, Siwei Sun, Danping Shi, Lei Hu
ePrint ReportFabrice Benhamouda, Shai Halevi, Lev Stambler
ePrint ReportTo do better, we investigate a relaxation, $(\alpha, \beta)$-ramp weighted secret sharing, where subsets of weight $\beta W$ can recover the secret (with $W$ the total weight), but subsets of weight $\alpha W$ or less cannot learn anything about it. We give two distinct types of constructions. The first is based on simple rounding, and has a share size which is linear in the number of parties and in $1/\epsilon$ (where $\epsilon=\beta-\alpha$).
The second type of schemes is based on a novel connection between weighted secret sharing and wiretap channels. We observe that for certain additive-noise $(\mathcal{R},\mathcal{A})$ wiretap channels, any semantically secure scheme can be naturally transformed into an $(\alpha,\beta)$-ramp weighted secret-sharing, where $\alpha,\beta$ are essentially the respective capacities of the channels $\mathcal{A},\mathcal{R}$. These constructions eliminate or reduce the dependence on the number of parties, at the price of increased dependence on $1/\epsilon$. We present two instantiations of this type of construction, one using Binary Symmetric wiretap Channels, and the other using additive Gaussian Wiretap Channels.
Tomer Ashur, Al Kindi, Willi Meier, Alan Szepieniec, Bobbin Threadbare
ePrint ReportCarla Ràfols, Alexandros Zacharakis
ePrint ReportDaniel Nager
ePrint ReportAnita Aghaie, Amir Moradi, Johannes Tobisch, Nils Wisiol
ePrint ReportFei Tang, Guowei Ling, Chaochao Cai, Jinyong Shan, Xuanqi Liu, Peng Tang, Weidong Qiu
ePrint ReportThis paper proposes an efficient algorithm called $\mathsf{FastECDLP}$ for solving the small exponential ECDLP at $128$-bit security level. We perform a series of deep optimizations from two points: computation and memory overhead. These optimizations ensure efficient decryption when the plaintext length $\ell$ is as long as possible in practice. Moreover, we also provide a concrete implementation and apply $\mathsf{FastECDLP}$ to some specific applications. Experimental results show that $\mathsf{FastECDLP}$ is far faster than the previous works. For example, the decryption can be done in $0.35$ ms with a single thread when $\ell = 40$, which is about $30$ times faster than that of Paillier. Furthermore, we experiment with $\ell$ from $32$ to $54$, and the existing works generally only consider $\ell \leq 32$. The decryption only requires $1$ second with $16$ threads when $\ell = 54$. In the practical applications, we can speed up model training of existing vertical federated learning frameworks by $4$ to $14$ times. At the same time, the decryption efficiency is accelerated by about $140$ times in a blockchain financial system (ESORICS 2021) with the same memory overhead.
Chanki Kim, Young-Sik Kim, Jong-Seon No
ePrint ReportPeter Gaži, Ling Ren, Alexander Russell
ePrint ReportThis article develops explicit, rigorous settlement bounds for proof-of-stake longest-chain protocols, placing them on equal footing with their proof-of-work counterparts. Our techniques apply with some adaptations also to the proof-of-work setting where they provide improvements to the state-of-the-art settlement bounds for proof-of-work protocols.
Lione, Francia, 22 April - 23 April 2023
Event CalendarSubmission deadline: 1 March 2023
Notification: 17 April 2023
Sousse, Tunisia, 19 July - 21 July 2023
Event CalendarSubmission deadline: 26 February 2023
Paris cedex 12, France, 23 April - 28 April 2023
Event CalendarSubmission deadline: 30 November 2022
Notification: 15 January 2023
University of Washington Tacoma
Job PostingClosing date for applications:
Contact: Questions related to this position are to be directed to the search committee chair, Dr. Wes J. Lloyd, at wlloyd@uw.edu.
More information: http://apply.interfolio.com/116931
University College Cork, Ireland
Job PostingTwo doctoral positions in cryptography and privacy are open in the Security Group at University College Cork (UCC), Ireland. Both positions are fully funded through research grants.
The first PhD will investigate adaptive privacy-preservation in IoT, and is funded by a Science Foundation Ireland grant (part of the CONNECT Centre). Research work will focus on local differential privacy and homomorphic encryption in IoT settings.
The second PhD will investigate anonymity and privacy of health data, and how they can be securely shared across different European health system. The position is funded by the EU Horizon Europe SECURED project. Research will focus on statistical re-identification attacks on anonymous health datasets. It will also explore privacy-preserving synthetic data generation.
Candidates should have a background/strong interest in security and privacy, as well as a good grasp of mathematics. Previous experience in cryptography is an asset, but is not required. Applicants should hold a good honours undergraduate or Masters degree in computer science, computer engineering, mathematics, or other relevant subject.
The successful applicant will receive a tax-free stipend of €18,500 per annum for up to four years, and tuition fees will be covered by the grant. The Government of Ireland is currently reviewing PhD stipends, and it is likely that the stipend will increase to match inflation.
A research and travel budget is also available to present at international conferences, purchase equipment etc.
The PhDs will work under the supervision of Dr. Paolo Palmieri (and Dr. Hazel Murray, MTU, in the first project). They will join the thriving Security Group at UCC, where several other PhDs and PostDocs are carrying out related research, and will have the opportunity to collaborate with the group extensive network of international collaborations.
Deadline: November 22, but early applications are encouraged
Closing date for applications:
Contact: Please submit your application using the web form at the link above. Please include: a cover letter; an up to date CV; and university transcripts.
E-mail applications will not be considered, but informal inquiries are welcome, and can be sent to Dr. Paolo Palmieri at p.palmieri@cs.ucc.ie
More information: https://ucc.qualtrics.com/jfe/form/SV_dmVI6vyPTRwgs2G
Eindhoven Technical University (TU/e)
Job PostingPossible topics fall into the field of provable security with a focus on the construction of efficient cryptographic building blocks and protocols, including
- (post-quantum) secure key exchange and messaging protocols and
- (post-quantum) secure digital signatures and public key encryption in realistic security models
- impossibility results/lower bounds for provably secure constructions.
Requirements:
- a Master's degree (or equivalent) with excellent grades in computer science, mathematics, or IT security.
- strong mathematical and/or algorithmic/theoretical CS background.
- good knowledge of cryptography and provable security.
- good written and verbal communication skills in English (Dutch is not required).
To apply, prepare a single PDF file that includes a CV with a course list and grades. The application deadline is December 15th, 2022.
Applications and questions can be directed to s.schage@tue.nl.
Closing date for applications:
Contact: Sven Schäge
More information: https://www.tue.nl/en/research/research-groups/mathematics/discrete-mathematics/coding-theory-and-cryptology/
University of York, UK
Job PostingThe Department of Computer Science at the University of York has several PhD studentships available for exceptional Home (UK & Ireland) and Overseas students through the Doctoral Centre for Safe, Ethical and Secure Computing (SEtS).
The Cyber Security and Privacy Research Group at the Department calls for students who are interested in pursuing a PhD in the following topics:
- Security of New and Emerging Networks: including security of Internet of Things (IoT) devices and networks, security and safety in robotics and autonomous systems, security and safety of unmanned aerial vehicles (UAV), and security of underwater networks and communications,
- Usable Security and Privacy: Web measurement to analyse and combat web tracking, developing privacy-enhancing technologies. usable security and privacy, and human factors in cyber security and privacy,
- Applied Cryptography: Design and analysis of provably-secure cryptographic schemes and protocols, especially those that preserve or enhance privacy, and including but not limited to automated formal analysis and mechanisation of proofs of security protocols,
- Malware Analysis and Detection: including different types of malware, such as ransomware and spyware, malware targeting mobile platforms (e.g. Android) or industrial control systems and critical infrastructure,
- Machine Learning for IoT Security: Machine learning techniques for IoT behavioural fingerprinting and attack detection for network security, and
- Privacy-Preserving Machine Learning: Edge based machine learning systems such as federated learning, and how to quantify, control, and manage privacy in such systems.
The available projects are supervised by a combination of faculty members including Dr. Roberto Metere, Dr. Siamak F. Shahandashti, Dr. Vasileios Vasilakis, Dr. Yuchen Zhao, and Dr. Poonam Yadav.
For more information please visit https://docs.google.com/document/d/1VtrNtFG1zy54o0BzymHj56gY--YEw2ch3EG18gnb3Lc
Closing date for applications:
Contact: sets-csp-group@york.ac.uk
More information: https://docs.google.com/document/d/1VtrNtFG1zy54o0BzymHj56gY--YEw2ch3EG18gnb3Lc