[frost] EncodedFrostKey BorrowDecode and correct markers

nickfarrow commented 4 months ago

Implement BorrowDecode for EncodedFrostKey for use in Frostsnap.
Convenient helper impls for EncodedFrostKey.
- I was finding I had to call things like Into::<FrostKey<Normal>>::into(session_progress.encoded_key.clone()) everywhere, .into_frost_key() is nicer.
Fully allow zero polynomial coeffs in share_backup (mistakenly missed a few functions last PR).
Keygen local poly Scalars should be secret.

LLFourn commented 4 months ago

ConceptACK

LLFourn commented 4 months ago

I've pushed two commits:

3435eae4d1a2bb5432d73d68096ab43c6c59f323 to bump the MSRV so tests pass
e6e217e4b05bcebd6ee93bb7fead1daf69b1d3da to set the secret share to Scalar<Secret, Zero> and fix some misc things

One thing I noticed is that the shares index can be one u5 or 52 but nothing inbetween. I think it should be fine to allow it to be any length. I guess @nickfarrow didn't do this because it was tricky with the API (there is this convert_bits thing but it seems to be broken). It looks like it might be possible with the v0.10 branch.

LLFourn / secp256kfun

[frost] EncodedFrostKey BorrowDecode and correct markers #175