feat(num-complex serialization): add serialization for bootstrappingkeys (LWEBSK)

[AlexanderViand]

We were trying to save some time while experimenting by saving the key material to disk and just re-reading it rather than constantly re-generating it just to debug things but we ran into the issue that the BSKs weren't serializable.

When we added the serde traits that are on the other keys, we ran into the issue that complex64 wasn't serializable. However, num-complex does have serde support, it's just optional and fftw does not offer a feature to toggle serde support on. After some digging I came up with this somewhat ugly hack that loads num-complex with the serde feature before loading fftw.

Maybe there's a nicer way to do this and/or this has some issues that I don't see (apart from the obvious fact that this requires manually matching the version number between fftw's depenceny and this "override") since I'm not super experienced with rust.

However, if it is acceptable then here's a PR for it ;)

[aPere3]

Hey @AlexanderViand,

Thanks for the PR. It is indeed a pain point to generate those bootstrapping keys.

Can you modify the PR to merge into the develop branch instead ?

[AlexanderViand]

Can you modify the PR to merge into the develop branch instead ?

@aPere3 Done :)

[aPere3]

Thanks 🙂

Before accepting that, I'd like to make sure that we can not achieve the same using the derive for remote approach. I don't have time to check that right away, but I'll try and come back to you.

Also, just for your information, the next release should have a multi-threaded bootstrapping key generation, as well as a new fftw wrapper, with no dependency on num-complex.

[aPere3]

Hello @AlexanderViand ,

We added a proper serialization in #21. It should be in the next release.

[AlexanderViand]

@aPere3 Thanks, great to hear that!