Multi-key Fully Homomorphic Encryption from Additive Homomorphism

Abstract

Fully homomorphic encryption (FHE) allows direct computations over the encrypted data without access to the decryption. Hence multi-key FHE is well suitable for secure multiparty computation. Recently, Brakerski et al. (TCC 2019 and EUROCRYPT 2020) utilized additively homomorphic encryption to construct FHE schemes with different properties. Motivated by their work, we are attempting to construct multi-key FHE schemes via additively homomorphic encryption. In this paper, we propose a general framework of constructing multi-key FHE, combining the additively homomorphic encryption with specific multiparty computation protocols constructed from encryption switching protocol. Concretely, every involved party encrypts his plaintexts with an additively homomorphic encryption under his own public key. Then the ciphertexts are evaluated by suitable multiparty computation protocols performed by two cooperative servers without collusion. Furthermore, an instantiation with an ElGamal variant scheme is presented. Performance comparisons show that our multi-key FHE from additively homomorphic encryption is more efficient and practical.

Enhancing Privacy in Large Language Model with Homomorphic Encryption and Sparse Attention

“…To address this, they further introduced multi-dataset fully homomorphic authenticated encryption (MDFHAE), achieving privacy protection with high efficiency. Xu et al proposed a general framework for constructing multi-key FHE, evaluating ciphertexts through appropriate computational protocols, but the practicality of the model remains an issue [18]. Zhang et al constructed Quantum Fully Homomorphic Encryption (QFHE) schemes against quantum computing, proposing two QFHE schemes: single-qubit point obfuscation and multi-qubit point obfuscation.…”