Robust Decentralized Multi-client Functional Encryption: Motivation, Definition, and Inner-Product Constructions

Yamin Li, Jianghong Wei, Fuchun Guo, Willy Susilo, Xiaofeng Chen

Abstract: Decentralized Multi-Client Functional Encryption (DMCFE) is a multi-user extension of Functional Encryption (FE) without relying on a trusted third party. However, a fundamental requirement for DMCFE is that the decryptor must collect the partial functional keys and the ciphertexts from all clients. If one client does not generate the partial functional key or the ciphertext, the decryptor cannot obtain any useful information. We found that this strong requirement limits the application of DMCFE in scenarios such as statistical analysis and machine learning.