Cryptology ePrint Archive: Report 2019/1082

On the Security of Multikey Homomorphic Encryption

Hyang-Sook Lee and Jeongeun Park

Abstract: Multikey fully homomorphic encryption (MFHE) scheme enables homomorphic computation on data encrypted under different keys. To decrypt a result ciphertext, all the involved secret keys are required. For multi decryptor setting, decryption is a protocol with minimal interaction among parties. However, all prior schemes supporting the protocol are not secure in public channel against a passive external adversary who can see any public information not joining the protocol. Furthermore, the possible adversaries have not been defined clearly.

In this paper, we revisit the security of MFHE and present a secure one-round decryption protocol. We apply it to one of existing schemes and prove the scheme is secure against possible static adversaries. As an application, we construct a two round multiparty computation without common random string.

Category / Keywords: cryptographic protocols / security of MFHE, MPC without CRS, Multikey homomorphic encryption.

Original Publication (with minor differences): IMA CC 2019

Date: received 22 Sep 2019, last revised 21 Dec 2020

Contact author: jungeun7430 at naver com

Available format(s): PDF | BibTeX Citation

Version: 20201222:065040 (All versions of this report)

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