Investigate how to integrate "Accurate and Composable Noise Estimates for CKKS with Application to Exact HE Computation"

Paper link:

Their code: https://github.com/tuneinsight/ckks-noise-estimator

Notable features:

* Noise estimation for bootstrapping
* Fix noise estimation for multiplication, so #1685 can be updated

> In this work, we develop a noise model that allows for tight estimates of the precision
loss, and propose a tool prototype for computing these estimates on any given circuit.
Our noise model relies on a novel definition, the component-wise noise, which makes
the average-case noise estimates tighter and more composable. As a result, our model
and tool can derive accurate estimates of complex circuits such as bootstrapping.
We experimentally demonstrate the tightness of our noise estimates by showing that
our theoretical estimates never deviate by more than 0.01 bits from experimental
estimates, even for large circuits, and hold with high probability. Furthermore, we
demonstrate how to apply our techniques to obtain an exact version of the CKKS
scheme in which the decryption removes all the noise (with high probability). Such
a scheme has many applications, as it allows to take advantage of the efficiency of
CKKS, while preserving an exact message space, hence further strengthening CKKS
against IND-CPA-D attacks.