Using threshold secret sharing, we propose a solution tailored for forgetful clients (i.e., not required to keep any cryptographic secret) while accommodating the dynamic nature of multi-cloud deployments. Furthermore, we delegate the computation ...$\mathsf{}$$\mathsf{}$$\mathsf{}$$\mathsf{}$

A zero-knowledge proof (ZKP) allows a prover to prove to a verifier that it knows some secret, such as a solution to a difficult puzzle, without revealing any information about it. In recent years, ZKP protocols using only a deck of playing cards ...

Attribute-Based Encryption ($\mathsf{ABE}$) stands as a cryptographic cornerstone, enabling access control to messages based on user attributes. The security definition of standard $\mathsf{ABE}$ is shown to be impossible in Universal Composability (UC) against an ...$\mathsf{}$$\mathsf{}$$\mathsf{}$$\mathsf{}$${\mathcal{}}_{\mathsf{}}$$\mathsf{}$$$$\mathsf{}$${\mathcal{}}_{\mathsf{}}$$\mathsf{}$$\mathsf{}$

Digital ticketing systems typically offer ticket purchase, refund, validation, and, optionally, anonymity of users. However, it would be interesting for users to transfer their tickets, as is currently done with physical tickets. We propose Applause, a ...

We consider swarms of luminous myopic opaque robots that run in synchronous Look-Compute-Move cycles. These robots have no global compass, but agree on a common chirality. In this context, we propose optimal solutions to the perpetual exploration ...

• Exploring a finite grid is not possible with only two disoriented oblivious robots.
• Exploring a finite grid is not possible with only three disoriented oblivious robots and visibility range 1.
• Exploring a finite grid is possible ...

We study perpetual torus exploration for swarms of autonomous, anonymous, uniform, and luminous robots. We consider robots with only few capabilities. They have a finite limited vision (myopic), they can only see robots at distance one or two. We ...

• We define the perpetual exploration problem on Torus graphs by simple mobile robots.
• We prove that the problem is not solvable with only two robots with limited visibility.
• We give optimal algorithms under visibility 1 and 2, and ...

Proving to someone else the knowledge of a secret without revealing any of its information is an interesting feature in cryptography. The best solution to solve this problem is a Zero-Knowledge Proof (ZKP) protocol.

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A zero-knowledge proof (ZKP) allows a party to prove to another party that it knows some secret, such as the solution to a difficult puzzle, without revealing any information about it. We propose a physical zero-knowledge proof using only a deck ...

We tackle the problem of secure cumulative reward maximization in multi-armed bandits in a cross-silo federated learning setting. Under the orchestration of a central server, each data owner participating at the cumulative reward computation has the ...

Post-Compromise Security (PCS) is a property of secure-channel establishment schemes, which limits the security breach of an adversary that has compromised one of the end-point to a certain number of messages, after which the channel heals. An attractive ...

CG:SHOP is an annual geometric optimization challenge and the 2022 edition proposed the problem of coloring a certain geometric graph defined by line segments. Surprisingly, the top three teams used the same technique, called conflict optimization. This ...

Trick-taking games are traditional card games played all over the world. There are many such games, and most of them can be played online through dedicated applications, either for fun or for betting money. However, these games have an intrinsic ...

Private permissioned blockchains are becoming gradually more sought-after. Such systems are reachable by authorized users, and tend to be completely transparent to whoever interacts with the blockchain. In this paper, we mitigate the latter. Authorized ...

The verification of computations performed by an untrusted server is a cornerstone for delegated computations, especially in multi-clients setting where inputs are provided by different parties. Assuming a common secret between clients, a garbled circuit ...

The stochastic multi-armed bandit is a classical reinforcement learning model, where a learning agent sequentially chooses an action (pull a bandit arm) and the environment responds with a stochastic reward drawn from an unknown distribution associated ...

We consider the problem of cumulative reward maximization in multi-armed bandits. We address the security concerns that occur when data and computations are outsourced to an honest-but-curious cloud i.e., that executes tasks dutifully, but tries to gain ...

Blind signatures are well-studied building blocks of cryptography, originally designed to enable anonymity in electronic voting and digital banking. Identity-based signature were introduced by Shamir in 1984 and gave an alternative to prominent ...$\mathsf{}$$\mathsf{}$$\mathsf{}$

Recent works to improve privacy in permissioned blockchains like Hyperledger Fabric rely on Idemix, the only anonymous credential system that has been integrated to date. The current Idemix implementation in Hyperledger Fabric (v2.4) only supports ...

Attack generation from an abstract model of a protocol is not an easy task. We present BIFROST (Bifrost Implements Formally Reliable prOtocols for Security and Trust), a tool that takes an abstract model of a cryptographic protocol and outputs an ...

Proving to someone else the knowledge of a secret without revealing any of its information is an interesting feature in cryptography. The best solution to solve this problem is a Zero-Knowledge Proof (ZKP) protocol.

Nurimisaki is a Nikoli puzzle. ...