## CryptoDB

### Matteo Campanelli

#### Publications

Year
Venue
Title
2020
ASIACRYPT
Vector commitments with subvector openings (SVC) [Lai-Malavolta, Boneh-Bunz-Fisch; CRYPTO'19] allow one to open a committed vector at a set of positions with an opening of size independent of both the vector's length and the number of opened positions. We continue the study of SVC with two goals in mind: improving their efficiency and making them more suitable to decentralized settings. We address both problems by proposing a new notion for VC that we call \emph{incremental aggregation} and that allows one to merge openings in a succinct way an \emph{unbounded} number of times. We show two applications of this property. The first one is immediate and is a method to generate openings in a distributed way. The second application is an algorithm for faster generation of openings via preprocessing. We then proceed to realize SVC with incremental aggregation. We provide two constructions in groups of unknown order that, similarly to that of Boneh et al. (which supports aggregating only once), have constant-size public parameters, commitments and openings. As an additional feature, for the first construction we propose efficient arguments of knowledge of subvector openings which immediately yields a keyless proof of storage with compact proofs. Finally, we address a problem closely related to that of SVC: storing a file efficiently in completely decentralized networks. We introduce and construct \emph{verifiable decentralized storage} (VDS), a cryptographic primitive that allows to check the integrity of a file stored by a network of nodes in a distributed and decentralized way. Our VDS constructions rely on our new vector commitment techniques.
2018
TCC
This paper initiates a study of Fine Grained Secure Computation: i.e. the construction of secure computation primitives against “moderately complex” adversaries. We present definitions and constructions for compact Fully Homomorphic Encryption and Verifiable Computation secure against (non-uniform) $\mathsf {NC}^1$ adversaries. Our results do not require the existence of one-way functions and hold under a widely believed separation assumption, namely $\mathsf {NC}^{1}\subsetneq \oplus \mathsf {L}/ {\mathsf {poly}}$ . We also present two application scenarios for our model: (i) hardware chips that prove their own correctness, and (ii) protocols against rational adversaries potentially relevant to the Verifier’s Dilemma in smart-contracts transactions such as Ethereum.

#### Coauthors

Dario Fiore (1)
Rosario Gennaro (1)
Nicola Greco (1)
Dimitris Kolonelos (1)
Luca Nizzardo (1)