Evaluate a floor (rounding) function on an LWE ciphertext

Performs the LWE equivalent of floor(ct / 2^roundbits) via functional bootstrapping. Used as a primitive in arbitrary- function evaluation pipelines where the bit-level rounding operation is needed separately from eval_func()'s LUT path.

Usage

eval_floor(ctx, ct, roundbits)

Arguments

ctx

A BinFHEContext

ct

An LWECiphertext

roundbits

Integer; the number of low-order bits to round off.

Value

A new LWECiphertext holding the rounded value.

Details

Binding-level note: the underlying BinFHEContext__EvalFloor cpp11 binding has been present since the earliest BinFHE work; the R wrapper was added later to close the latent gap (cpp11-only entry with no R path).

See also

eval_func(), eval_sign()