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Roberta De Viti

Publications and source records attributed to Roberta De Viti.

6 recordsLinked to original sources
arXiv2026

Semantic Recall for Vector Search

We introduce Semantic Recall, a novel metric to assess the quality of approximate nearest neighbor search algorithms by considering only semantically relevant objects that are theoretically retrievable via exact nearest neighbor search. Unlike traditional recall, semantic recall does not penalize algorithms for failing to retrieve objects that are semantically irrelevant to the query, even if those objects are among their nearest neighbors. We demonstrate that semantic recall is particularly useful for assessing retrieval quality on queries that have few relevant results among their nearest neighbors-a scenario we uncover to be common within embedding datasets. Additionally, we introduce Tolerant Recall, a proxy metric that approximates semantic recall when semantically relevant objects cannot be identified. We empirically show that our metrics are more effective indicators of retrieval quality, and that optimizing search algorithms for these metrics can lead to improved cost-quality tradeoffs.

cs.IR↗
arXiv2025

SoK: Demystifying the multiverse of MPC protocols

This paper systematizes knowledge on the performance of Multi-Party Computation (MPC) protocols. Despite strong privacy and correctness guarantees, MPC adoption in real-world applications remains limited by high costs (especially in the malicious setting) and lack of guidance on choosing suitable protocols for concrete workloads. We identify the theoretical and practical parameters that shape MPC efficiency and conduct an extensive experimental study across diverse benchmarks. Our analysis discusses the trade-offs between protocols, and highlights which techniques align best with different application scenarios and needs. By providing actionable guidance for developers and outlining open challenges for researchers, this work seeks to narrow the gap between MPC theory and practice.

cs.CR↗
arXiv2025

The Role of Privacy Guarantees in Voluntary Donation of Private Health Data for Altruistic Goals

The voluntary donation of private health information for altruistic purposes, such as supporting research advancements, is a common practice. However, concerns about data misuse and leakage may deter people from donating their information. Privacy Enhancement Technologies (PETs) aim to alleviate these concerns and in turn allow for safe and private data sharing. This study conducts a vignette survey (N=494) with participants recruited from Prolific to examine the willingness of US-based people to donate medical data for developing new treatments under four general guarantees offered across PETs: data expiration, anonymization, purpose restriction, and access control. The study explores two mechanisms for verifying these guarantees: self-auditing and expert auditing, and controls for the impact of confounds including demographics and two types of data collectors: for-profit and non-profit institutions. Our findings reveal that respondents hold such high expectations of privacy from non-profit entities a priori that explicitly outlining privacy protections has little impact on their overall perceptions. In contrast, offering privacy guarantees elevates respondents' expectations of privacy for for-profit entities, bringing them nearly in line with those for non-profit organizations. Further, while the technical community has suggested audits as a mechanism to increase trust in PET guarantees, we observe limited effect from transparency about such audits. We emphasize the risks associated with these findings and underscore the critical need for future interdisciplinary research efforts to bridge the gap between the technical community's and end-users' perceptions regarding the effectiveness of auditing PETs.

cs.CR↗
arXiv2024

ProLoc: Robust Location Proofs in Hindsight

Many online services rely on self-reported locations of user devices like smartphones. To mitigate harm from falsified self-reported locations, the literature has proposed location proof services (LPSs), which provide proof of a device's location by corroborating its self-reported location using short-range radio contacts with either trusted infrastructure or nearby devices that also report their locations. This paper presents ProLoc, a new LPS that extends prior work in two ways. First, ProLoc relaxes prior work's proofs that a device was at a given location to proofs that a device was within distance "d" of a given location. We argue that these weaker proofs, which we call "region proofs", are important because (i) region proofs can be constructed with few requirements on device reporting behavior as opposed to precise location proofs, and (ii) a quantitative bound on a device's distance from a known epicenter is useful for many applications. For example, in the context of citizen reporting near an unexpected event (earthquake, violent protest, etc.), knowing the verified distances of the reporting devices from the event's epicenter would be valuable for ranking the reports by relevance or flagging fake reports. Second, ProLoc includes a novel mechanism to prevent collusion attacks where a set of attacker-controlled devices corroborate each others' false locations. Ours is the first mechanism that does not need additional infrastructure to handle attacks with made-up devices, which an attacker can create in any number at any location without any cost. For this, we rely on a variant of TrustRank applied to the self-reported trajectories and encounters of devices. Our goal is to prevent retroactive attacks where the adversary cannot predict ahead of time which fake location it will want to report, which is the case for the reporting of unexpected events.

cs.CR↗
arXiv2024

CoVault: A Secure Analytics Platform

Analytics on personal data, such as individuals' mobility, financial, and health data can be of significant benefit to society. Such data is already collected by smartphones, apps and services today, but liberal societies have so far refrained from making it available for large-scale analytics. Arguably, this is due at least in part to the lack of an analytics platform that can secure data through transparent, technical means (ideally with decentralized trust), enforce source policies, handle millions of distinct data sources, and run queries on billions of records with acceptable query latencies. To bridge this gap, we present an analytics platform called CoVault which combines secure multi-party computation (MPC) with trusted execution environment (TEE)-based delegation of trust to be able execute approved queries on encrypted data contributed by individuals within a datacenter to achieve the above properties. We show that CoVault scales well despite the high cost of MPC. For example, CoVault can process data relevant to epidemic analytics for a country of 80M people (about 11.85B data records/day) on a continuous basis using a core pair for every 20,000 people. Compared to a state-of-the-art MPC-based platform, CoVault can process queries between 7 to over 100 times faster, as well as scale to many sources and big data.

cs.CR↗