Hardening Cassandra against Byzantine failures

Cassandra is one of the most widely used distributed data stores. In this work, we analyze Cassandra's vulnerabilities when facing Byzantine failures and propose protocols for hardening Cassandra against them. We examine several alternative design choices and compare between them both qualitatively and empirically by using the Yahoo! Cloud Serving Benchmark (YCSB) performance benchmark. Some of our proposals include novel combinations of quorum access protocols with MAC signatures arrays and elliptic curve public key cryptography so that in the normal data path, there are no public key verifications and only a single relatively cheap elliptic curve signature made by the client. Yet, these enable data recovery and authentication despite Byzantine failures and across membership configuration changes. In the experiments, we demonstrate that our best design alternative obtains roughly half the performance of plain (non-Byzantine) Cassandra.