Dynamic Volume-Hiding Encrypted Multi-Maps with Applications to Searchable Encryption

We study encrypted storage schemes where a client outsources data to an untrusted third-party server (such as cloud provider) while maintaining the ability privately query and dynamically update data. focus on multi-maps (EMMs), structured encryption (STE) scheme that stores pairs of label value tuples. EMMs allow queries labels return associated tuple. As responses are variable-length, subject volume leakage attacks introduced by Kellaris et al. [CCS'16]. To prevent these attacks, volume-hiding were Kamara Moataz [Eurocrypt'19] hide volumes (i.e., tuple lengths). our main contribution, we present first fully dynamic both asymptotically concretely efficient. Furthermore, they simultaneously forward backward private which de-facto standard security notions for STE schemes. Additionally, implement showcase their concrete efficiency. Our experimental evaluations show constructions able add dynamicity with minimal no additional cost compared prior best static Patel [CCS'19].