BABE implementation

[kwanCCC]

First important thing is VRF, We will use the Schnorrkel VRF and sr25519 signatures. But I'm not sure about the BLS because most BLS makes hashing-to-the-curve slow.

• Digest in Block Header (Primary, Secondary)
• The API of VRF(epoch_randomness, slot_num)
• Distribute Clock system
• block proposing
• block verification

[keyvank]

@kwanCCC Do you want to implement VRFs from scratch? I think a good strategy is to make abstract traits of signatures, VRFs and all other crypto primitives (Like what I did here: https://github.com/zeeka-network/bazuka/blob/master/src/crypto.rs ) and then use prewritten libraries to implement these traits. This way we can make a MVP faster, then if we figured out we don't want to use those VRF libraries, we can just implement those traits again ourselves. I was going to using https://github.com/witnet/vrf-rs library as our VRF backend. It uses secp256k1 curves. Is that ok? Or am I missing something?

[kwanCCC]

@keyvank
No,I don't want implement VRFs from scratch. And I found schnorrkel, but only support Ristretto compressed Ed25519 points. The task VRF which one hasn't clear description described above. The goal of VRF is make it as part of KeyStore which works as a module in whole system then we can use KeyStore to sign a value using VRF, verify a proof.

[kwanCCC]

pub trait CryptoStore {
  fn generate_new_keypair();
  fn sign_with(msg);
  fn vrf_sign();
  .......
}

The Api of KeyStore maybe like this or some more methods.