Information Flows in Encrypted Databases

TL;DR

SecureSQL is a system that partitions query processing between untrusted servers and trusted clients in encrypted databases, preventing information leaks during query execution with minimal overhead for explicit flows.

Contribution

It introduces SecureSQL, a novel approach that ensures confidentiality by preventing information flows during query processing in encrypted databases.

Findings

Protects against explicit information flows with less than 30% overhead.

Protecting against implicit flows incurs higher costs and complexity.

Partitioning query processing enhances security in encrypted databases.

Abstract

In encrypted databases, sensitive data is protected from an untrusted server by encrypting columns using partially homomorphic encryption schemes, and storing encryption keys in a trusted client. However, encrypting columns and protecting encryption keys does not ensure confidentiality - sensitive data can leak during query processing due to information flows through the trusted client. In this paper, we propose SecureSQL, an encrypted database that partitions query processing between an untrusted server and a trusted client while ensuring the absence of information flows. Our evaluation based on OLTP benchmarks suggests that SecureSQL can protect against explicit flows with low overheads (< 30%). However, protecting against implicit flows can be expensive because it precludes the use of key databases optimizations and introduces additional round trips between client and server.