Reference : Concise UC Zero-Knowledge Proofs for Oblivious Updatable Databases
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Engineering, computing & technology : Computer science
Computational Sciences
Concise UC Zero-Knowledge Proofs for Oblivious Updatable Databases
Camenisch, Jan [Dfinity]
Dubovitskaya, Maria [Dfinity]
Rial Duran, Alfredo mailto [University of Luxembourg > Interdisciplinary Centre for Security, Reliability and Trust (SNT) > >]
[en] vector commitments ; universal composability ; modular design
[en] We propose an ideal functionality $\Functionality_{\COMD}$ and a construction for oblivious and updatable committed databases.
$\Functionality_{\COMD}$ allows a prover to read, write, and update values in a database and to prove to a verifier in zero-knowledge that a value is read from or written into a certain position.
The following properties must hold:
(1) values stored in the database remain hidden from the verifier;
(2) a value read from a certain position is equal to the value previously written into that position;
(3) (obliviousness) both the value read or written and its position remain hidden from the verifier.

We describe a construction for $\Functionality_{\COMD}$ based on vector commitments.
After the initialization phase, the cost of zero-knowedge proofs for reading and writing is independent of the database size,
outperforming other techniques that achieve cost sublinear in the dataset size for prover and/or verifier.
Therefore, our construction is especially appealing for cases with large datasets.

Finally, we show how to use $\Functionality_{\COMD}$ as a building block in ``commit-and-prove'' two-party protocols, i.e.\ protocols where the prover commits to her inputs and subsequently proves in zero-knowledge statements about the committed values. In comparison to simply using commitment schemes, our construction allows the prover to hide positions read or written efficiently, which is useful to design protocols for e.g.\ cloud-based services, blockchain, privacy-preserving location sharing services and e-commerce, and efficient OR proofs.
FnR ; FNR11650748 > Alfredo Rial > SZK > Stateful Zero-Knowledge > 01/03/2018 > 28/02/2021 > 2017

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