An Efficient Delegatable Order-Revealing Encryption Scheme for Multi-User Range Queries

To balance data confidentiality and availability, order-revealing encryption (ORE) has emerged as a pivotal primitive facilitating range queries on encrypted data. However, challenges arise in diverse user domains where data is encrypted with different keys, giving rise to the development of delegatable order-revealing encryption (DORE) schemes. Regrettably, existing DORE schemes are susceptible to authorization token forgery attacks and rely on computationally intensive bilinear pairings. This work proposes a novel solution to address these challenges. We first introduce a delegatable equality-revealing encryption scheme, enabling the comparison of ciphertexts encrypted by distinct secret keys through authorization tokens. Building upon this, we present a delegatable order-revealing encryption that leverages bitwise encryption. DORE supports efficient multi-user ciphertext comparison while robustly resisting authorization token forgery attacks. Significantly, our approach distinguishes itself by minimizing bilinear pairings. Experimental results highlight the efficacy of DORE, showcasing a notable speedup of $2.8\times$ in encryption performance and $1.33\times$ in comparison performance compared to previous DORE schemes, respectively.