Multi-Client Order-Revealing Encryption
This addresses a gap in cryptographic primitives for secure range queries on encrypted data from multiple sources, though it appears incremental as it extends existing single-client concepts.
The paper tackles the problem of comparing encrypted data from multiple clients, which previous order-revealing encryption schemes did not support, by proposing multi-client order-revealing encryption with defined security models and two specific schemes, implementing them and suggesting performance improvements.
Order-revealing encryption is a useful cryptographic primitive that provides range queries on encrypted data since anyone can compare the order of plaintexts by running a public comparison algorithm. Most studies on order-revealing encryption focus only on comparing ciphertexts generated by a single client, and there is no study on comparing ciphertexts generated by multiple clients. In this paper, we propose the concept of multi-client order-revealing encryption that supports comparisons not only on ciphertexts generated by one client but also on ciphertexts generated by multiple clients. We also define a simulation-based security model for multi-client order-revealing encryption. The security model is defined with respect to the leakage function which quantifies how much information is leaked from the scheme. Next, we present two specific multi-client order-revealing encryption schemes with different leakage functions in bilinear maps and prove their security in the random oracle model. Finally, we give the implementation of the proposed schemes and suggest methods to improve the performance of ciphertext comparisons.