Hi all,
I know that we can make secure comparisons using BinFHE. Is it possible to use BinFHE to add (or multiply) two encrypted integers?
Thank you!
For LWE ciphertexts, BinFHE supports addition and multiplication by a constant (standard methods for an additive HE scheme; see Program Listing for File lwe-pke.h — OpenFHE documentation for the API). Multiplication by an encrypted integer requires an SHE scheme, like Ring-GSW, which is not supported in BinFHE. Multiplication can be done at a bit level or using arbitrary function evaluation, but this would be too expensive. A more efficient way is to use scheme switching, where multiplications can be done using another scheme, like CKKS or BFV. Scheme switching for CKKS ↔ FHEW will be added in v1.1 (later this summer).
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