Augmenting Encrypted Search: A Decentralized Service Realization with Enforced Execution

Abstract

Searchable symmetric encryption (SSE) allows the data owner to outsource an encrypted database to a remote server in a private manner while maintaining the ability for selectively search. So far, most existing solutions focus on an honest-but-curious server, while security designs against a malicious server have not drawn enough attention. A few recent works have attempted to construct verifiable SSE that enables the data owner to verify the integrity of search results. Nevertheless, these verification mechanisms are highly dependent on specific SSE schemes, and fail to support complex queries. A general verification mechanism is desired that can be applied to all SSE schemes. In this work, instead of concentrating on a central server, we explore the potential of the smart contract, an emerging blockchain-based decentralized technology, and construct decentralized SSE schemes where the data owner can receive correct search results with assurance without worrying about potential wrongdoings of a malicious server. We study both public and private blockchain environments and propose two designs with a trade-off between security and efficiency. To better support practical applications, the multi-user setting of SSE is further investigated where the data owner allows authenticated users to search keywords in shared documents. We implement prototypes of our two designs and present experiments and evaluations to demonstrate the practicability of our decentralized SSE schemes.

A Blockchain-Based Normalized Searchable Encryption System for Medical Data

“…e few SSE schemes that support multiuser search also require the owner to calculate a search trapdoor [20] online. Multiuser searchable encryption (MUSE) [21] is a significant research content of SE with practical research significance.…”

“…Chen et al [29] used electronic medical record EHR file indexes to construct complex logical structures and store them on a blockchain so that data users can search the file indexes using these logical expressions. Hu et al [20] enabled users to search private databases in a blockchain environment and implement dynamic access control for searches. However, all of the above schemes outsource complex operations or encrypted data to the blockchain, which greatly degrades the performance of the system.…”

“…Performance Comparison. We compare the theoretical performance of our scheme with other multiuser searchable encryption schemes, where the MVSSE [24] and BAEKS [25] schemes are both based on public key cryptography, and Π + [20] is a symmetric searchable encryption scheme. In this study, we compare the computational overheads of the main algorithms of searchable encryption schemes, including encryption algorithm, trapdoor algorithm, and search algorithm.…”

A Fine-Grained Medical Data Sharing Scheme with Ciphertext Reencryption

“…In 2017, Liu et al [27] used private blockchain to ensure data integrity. In 2019, Hu et al [28] proposed a blockchain-based data sharing scheme, a decentralized system is established based on smart contracts.…”

“…In this section, the function and efficiency of the proposed scheme and other related schemes [19,20,23,24,28] are evaluated and compared. We compared the aforementioned 5 schemes with our scheme in terms of system functions.…”