International Association for Cryptologic Research: Achievable CCA2 Relaxation for Homomorphic Encryption

This paper, co-authored by the Algorand Foundation, tackles a critical challenge in securing computations on encrypted data. Homomorphic encryption, while powerful, suffers from expensive "bootstrapping" processes to refresh ciphertexts. To address this, some explored client-aided outsourcing, where a client refreshes ciphertexts for a server performing computations. However, a key question remains: is this approach vulnerable to malicious servers?

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