Extending Order Preserving Encryption for Multi-User Systems
Several Order Preserving Encryption (OPE) algorithms have been developed in the literature to support search on encrypted data. However, existing OPE schemes only consider a single encryption key, which is infeasible for a practical system with multiple users (implying that all users should have the single encryption key in order to encrypt or decrypt confidential data). In this paper, the authors develop the first protocols, DOPE and OE-DOPE, to support the use of OPE in multi-user systems. They introduce a group of key agents into the system and invent the DOPE protocol to enable "Distributed Encryption" to assure that the OPE encryption key is not known by any entity in the system.