Online surveys are frequently used to collect feedback on sensitive topics, yet most deployed platforms rely on authenticated accounts, cookies, or operator-enforced policies to protect anonymity and limit participation. These approaches offer limited protection against retrospective deanonymization in the event of database compromise. The anonymous survey primitive addresses this problem by enabling authenticated yet anonymous submissions with at-most-once participation per survey, without requiring a trusted setup. Current solutions may however be computationally demanding when aiming for large scale deployment. We revisit this primitive and present CAnonize, a new anonymous survey protocol that considerably improves the efficiency compared to the state of the art, while also relying on weaker computational assumptions and preserving a strong corruption model: our protocol relies solely on the SXDH assumption in asymmetric bilinear groups (q-type assumptions were used before), and offers unlinkability under adaptive corruption of the registration authority, survey authorities, and users, even under full transcript exposure and post-compromise database leakage. We confirm the efficiency benefits and practicality of CAnonize through a prototype implementation in Rust: using the BLS12-381 curves, the running times for submitting and processing a survey response are below 100ms for the user and for the survey authority.

This paper explores the interaction between receipt- freeness and cast-as-intended verifiability, a property that has been overlooked until now or assumed to be granted through procedural means in the context of receipt-free voting protocols.We first demonstrate that it is impossible to obtain a receipt-free voting protocol with cast-as-intended verifiability if the voting process is non-interactive, unless a trusted authority is available. We also demonstrate that, if a trusted voter registration authority is available, then cast-as-intended verifiability and receipt-freeness can be obtained.Furthermore, after extending standard receipt-freeness security definitions to an interactive voting (and corruption) setting, we demonstrate that the same security properties can be obtained using an interactive voting process.Finally, we discuss the performance of our protocols based on a prototype implementation.

Leakage resilience (LR) and misuse resistance (MR) are two important properties for the deployment of authenticated encryption (AE) schemes. They aim at mitigating the impact of implementation flaws due to side-channel leakages and misused randomness. In this paper, we discuss the interactions and incompatibilities between these two properties.

Digital signatures are perhaps the most important base for authentication and trust relationships in large scale systems. More specifically, various applications of signatures provide privacy and anonymity preserving mechanisms and protocols, and these, in turn, are becoming critical (due to the recently recognized need to protect individuals according to national rules and regulations). A specific type of signatures called "signatures with efficient protocols", as introduced by Camenisch and Lysyanskaya (CL), efficiently accommodates various basic protocols and extensions like zero-knowledge proofs, signing committed messages, or re-randomizability. These are, in fact, typical operations associated with signatures used in typical anonymity and privacy-preserving scenarios.