F-FHEW: High-Precision Approximate Homomorphic Encryption with Batch Bootstrapping

Man Chen, Yuyue Chen, Rui Zong, ZengPeng Li, Zoe L. Jiang

Abstract: Floating-point fully homomorphic encryption (FPFHE) supports arbitrary computation on ciphertexts and yields approximate results. On one hand, for the state-of-the-art, the CKKS-like scheme (Jutla et al., EUROCRYPT 2022) achieves a precision of 100-bit decimal as the messages originally include some encoding noise, as well as some additional errors will be generated by bootstrapping operation. Nonetheless, operations with higher precision are also appreciated by various kinds of applications, such as Semidefinite Programming requiring 128-bit precision. On the other hand, the CKKS-like scheme is very computationally intensive. Compared to processing the same data in clear, it is slower, less efficient, and more energy-consuming.