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stellar / slingshot

A new blockchain architecture under active development, with a strong focus on scalability, privacy and safety
Apache License 2.0
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schnorr signature scheme compatibility #382

Open oleganza opened 4 years ago

oleganza commented 4 years ago

Would be cool to make Schnorrkel and Starsig compatible with each other. Here's a table of differences.

  Starsig Schnorrkel Proposal
Domain separator "dom-sep", "starsig v1" "proto-name", "Schnorr-sig" "dom-sep", "schnorr-ristretto255"
Pubkey label "X" "sign:pk" "pk"
R label "R" "sign:R" "R"
Challenge label "c" "sign:c" "c"

Convenience wrapper for byte-oriented API:

  Starsig Schnorrkel Proposal
Transcript label "Starsig.sign_message" "SigningContext" "schnorr-ristretto255-message"
Customization append($label,$msg) append("", $label)
append("sign-bytes",$msg)		 append("msg",$msg)
burdges commented 4 years ago

I picked the "sign:" prefix because of https://github.com/w3f/schnorrkel/issues/39 In fact I believe that's not a serious concern, but adjusting seemed easier than checking any details at the time.

burdges commented 4 years ago

It's true "SigningContext" kinda sucks. :( I originally asked users to supply the label, but then this happened hastily: https://github.com/dalek-cryptography/merlin/pull/44

oleganza commented 4 years ago

Oh, i forgot about 'static slices for labels.

burdges commented 4 years ago

Inside the protocol 'static labels work fine, of course. It's just when dynamic languages want to create a transcript that you encounter problems: https://github.com/paritytech/schnorrkel-js/issues/12

As an aside, I needed this weirdness so that ed25519 and schnorrkel could be batch verified together.

oleganza commented 4 years ago

@burdges does it even make sense to provide $label parameter for plain message-oriented API? If one wants to get fancy with composition and domain-separation, they should use transcript directly, no? I'd keep it as simple as current signature schemes do - message in, signature out.

burdges commented 4 years ago

I suppose not really.. I wanted us to use stronger domain separation everywhere in polkadot, but others preferred Blake2 and no Blake2 STROBE variant exists, and we support other signature schemes too. Ideas leak. :P

burdges commented 4 years ago

Are all these commits sequenced identically?