International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Céline Chevalier

Publications

Year
Venue
Title
2023
TCC
Semi-Quantum Copy-Protection and More
Céline Chevalier Paul Hermouet Quoc-Huy Vu
Properties of quantum mechanics have enabled the emergence of quantum cryptographic protocols achieving important goals which are proven to be impossible classically. Unfortunately, this usually comes at the cost of needing quantum power from every party in the protocol, while arguably a more realistic scenario would be a network of classical clients, classically interacting with a quantum server. In this paper, we focus on copy-protection, which is a quantum primitive that allows a program to be evaluated, but not copied, and has shown interest especially due to its links to other unclonable cryptographic primitives. Our main contribution is to show how to dequantize quantum copy-protection schemes constructed from hidden coset states, by giving a construction for classically-instructed remote state preparation for coset states, which *preserves hardness properties of hidden coset states*. We then apply this dequantizer to obtain semi-quantum cryptographic protocols for copy-protection and tokenized signatures with strong unforgeability. In the process, we present the first secure copy-protection scheme for point functions in the plain model and a new direct product hardness property of coset states which immediately implies a strongly unforgeable tokenized signature scheme.
2022
EUROCRYPT
Embedding the UC Model into the IITM Model 📺
Daniel Rausch Ralf Kuesters Celine Chevalier
Universal Composability is a widely used concept for the design and analysis of protocols. Since Canetti's original UC model and the model by Pfitzmann and Waidner several different models for universal composability have been proposed, including, for example, the IITM model, GNUC, CC, but also extensions and restrictions of the UC model, such as JUC, GUC, and SUC. These were motivated by the lack of expressivity of existing models, ease of use, or flaws in previous models. Cryptographers choose between these models based on their needs at hand (e.g., support for joint state and global state) or simply their familiarity with a specific model. While all models follow the same basic idea, there are huge conceptually differences, which raises fundamental and practical questions: (How) do the concepts and results proven in one model relate to those in another model? Do the different models and the security notions formulated therein capture the same classes of attacks? Most importantly, can cryptographers re-use results proven in one model in another model, and if so, how? In this paper, we initiate a line of research with the aim to address this lack of understanding, consolidate the space of models, and enable cryptographers to re-use results proven in other models. As a start, here we focus on Canetti's prominent UC model and the IITM model proposed by K{\"u}sters et al. The latter is an interesting candidate for comparison with the UC model since it has been used to analyze a wide variety of protocols, supports a very general protocol class and provides, among others, seamless treatment of protocols with shared state, including joint and global state. Our main technical contribution is an embedding of the UC model into the IITM model showing that all UC protocols, security and composition results carry over to the IITM model. Hence, protocol designers can profit from the features of the IITM model while being able to use all their results proven in the UC model. We also show that, in general, one cannot embed the full IITM model into the UC model.
2016
PKC
2016
ASIACRYPT
2016
ASIACRYPT
2013
PKC
2013
CRYPTO
2013
ASIACRYPT
2009
PKC
2009
EUROCRYPT
2009
CRYPTO

Program Committees

PKC 2018