Practical q-IND-CPA-D-Secure Approximate Homomorphic Encryption

Abstract

At Eurocrypt 2021 Li and Micciancio presented a passive key recovery attack on CKKS, leveraging its approximate nature. They proposed a new security notion for approximate homomorphic encryption schemes: q-IND-CPA-D security. In their initial work they left achieving q-IND-CPA-D security for CKKS as an open problem, but they proposed two approaches: noise flooding and exact CKKS. This work addresses the latter approach: a truncated version of CKKS is proposed, where the bits polluted by the error are rounded off. It is shown that thus it is possible to achieve q-IND-CPA-D security for this truncated CKKS without too much loss in efficiency.

About the speaker

Lea is a third year PhD student at the Norwegian University of Technology and Science (NTNU). Her main research area is Fully Homomorphic Encryption.

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