Abstract

In this paper, we shall present compact certificate schemes, which allow parties to take a large number of signatures on a message M, by many signers of different weights, and compress them to a much shorter certificate. This certificate convinces the verifiers that signers with sufficient total weight signed M, even though the verifier will not see—let alone verify—all of the signatures. Thus, for example, a compact certificate can be used to prove that parties who jointly have a sufficient total account balance have attested to a given block in a blockchain. Evaluation shows that compact certificates are 50–280× smaller and 300–4000× cheaper to verify than a natural baseline approach.

Bio

Giorgos Tsimos is an Electrical Engineering PhD student at the Maryland Cybersecurity Center (MC2) at UMD, advised by Prof. Charalampos (Babis) Papamanthou. Before that, he completed his B.S. and M.S. in Computer Science at AUEB, Greece. He is interested in Applied Cryptography, mainly how to construct more efficient and secure Consensus Protocols, as well as current problems related to Blockchains.

Abstract

In this paper, we consider privacy-preserving update strategies for secure outsourced growing databases. Such databases allow append-only data updates on the outsourced data structure while analysis is ongoing. Despite a plethora of solutions to securely outsource database computation, existing techniques do not consider the information that can be leaked via update patterns. To address this problem, we design a novel secure outsourced database framework for growing data, DP-Sync, which interoperates with a large class of existing encrypted databases and supports efficient updates, while providing differentially-private guarantees for any single update. We demonstrate DP-Sync's practical feasibility in terms of performance and accuracy with extensive empirical evaluations on real world datasets.

Bio

Johes Bater is a postdoctoral researcher in the Database Group at Duke University hosted by Prof. Ashwin Machanvajjhala and Prof. Kartik Nayak. Before that, he completed his Ph.D. in Computer Science at Northwestern University under the guidance of Prof. Jennie Rogers and his B.S. and M.S. in Electrical Engineering at Stanford University. His research centers on how to implement privacy and security in database systems. By investigating the intersection of security, privacy, and performance, he hopes to build fast, accurate database systems that support privacy-preserving analytics with provable security guarantees.