Blind BBS Signatures

[BasileiosKal]

New (updated) draft on blind signatures: https://basileioskal.github.io/blind-bbs-signatures/draft-bbs-blind-signatures.html

Couple notes:

• It seems that the commitment value added in CoreSign in the main draft is not useful after all. Will probably remove it.
• If agreed, the above would probably replace the current draft and hopefully be submitted at the IETF as well.
• Will add test vectors soon.

[BasileiosKal]

Fixtures added: https://github.com/BasileiosKal/blind-bbs-signatures/tree/main/fixtures/fixture_data