Implement loading of trusted setup

[joebebel]

If KZG commitments are used, then a trusted setup has to be loaded (probably an existing setup, Zcash or Filecoin)

This is a straightforward task, implement in Rust the download/verification/loading of the trusted setup. Ideally there should be extensive opportunity for code reuse/external crates here, since for example Zcash clients perform this task exactly.

[ggkitsas]

https://github.com/zcash/librustzcash/blob/master/zcash_proofs/src/lib.rs
https://github.com/arkworks-rs/poly-commit/blob/master/src/kzg10/mod.rs

[joebebel]

This code can probably be modified to do a powers of tau setup for BLS12-377 if needed:

https://github.com/arielgabizon/perpetualpowersoftau

[ggkitsas]

Update:

temporarily hosting our effort here https://github.com/heliaxdev/trusted-setup/

So far:

• deserialize and load the powers-of-tau as hosted by zcash (https://download.z.cash/downloads/powersoftau/)
  • testing if deserialization is performed correctly
  • not able to map params appropriatelly to make KZG work
• used https://github.com/ebfull/powersoftau/ to generate parameters with known tau to help in further examination/debugging
  • deserialized them

[ggkitsas]

• Downloading the KZG parameters is implemented here: https://github.com/heliaxdev/trusted-setup/blob/master/src/lib.rs#L119
• The KZG parameters file is a preprocessed (for efficiency reasons) file from the powersoftau (this is the download link). The process is described here for verification and replicability
• Loading the parameters is implemented here: https://github.com/heliaxdev/trusted-setup/blob/master/src/lib.rs#L156