Introduce Schnorr signature

[kseo]

It's ready now.

[kseo]

Some preparation patches were landed: 6359ab0, 9a78f45, c4f49a8, 37a34b8, 418d472, 94ef1e6, 0990b70, 6e78e95

[hyunsikjeong]

To-do

• Read the issues in libsecp256k1 which are related to Schnorr signature.
• Make a demo for Schnorr signature.
• Implement Schnorr signature in the CodeChain primitives and the SDK.

[hyunsikjeong]

Finished working on the primitives.

[hyunsikjeong]

Finished working on CodeChain and the SDK.
CodeChain: https://github.com/CodeChain-io/codechain/commits/schnorr
codechain-sdk-js: https://github.com/codechain-io/codechain-sdk-js/tree/schnorr
codechain-keystore-js: https://github.com/CodeChain-io/codechain-keystore-js/tree/schnorr

[hyunsikjeong]

Might need to change the code of libsecp256k1. See https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#cite_note-4, the current code uses the option 2.

[sgkim126]

@jhs7jhs What is the current status of this issue? Is there something to do?

[hyunsikjeong]

@sgkim126 Currently the basic implementation is finished, but it's based on the experimental part of the old version of the bitcoin library, so it is quite dangerous to merge. Also, MuSig signing is not supported yet and needs to be implemented.