# Re-using KZG ceremony

## New additions:
- https://github.com/availproject/avail-srs/tree/main

## Parsing Ethereum's KZG ceremony

- Use existing sequencer data
- https://kzg-ceremony-sequencer-dev.fly.dev/info/status
- https://github.com/ethereum/kzg-ceremony-specs/blob/master/apiSpec/sequencerApi.yml#L36
- `BatchTranscript` contains 4 sub ceremonies, `Transcript` elements
- Parse `Transcript`:

Transcript:
  type: object
  description: Current transcript
  properties:
    numG1Powers:
      type: number
      format: int32
    numG2Powers:
      type: number
      format: int32
    powersOfTau:
      type: object
      properties:
        G1Powers:
          type: array
          items:
            type: string
        G2Powers:
          type: array
          items:
            type: string
      required:
        - G1Powers
        - G2Powers
    witness:
      type: object
      properties:
        runningProducts:
          type: array
          items:
            type: string
        potPubkeys:
          type: array
          items:
            type: string
      required:
        - runningProducts
        - potPubkeys

- Looking into this super [neat lib](https://github.com/heliaxdev/kzg-setup-powersoftau) now
- It gives me (`[G1], VerifierKey`) instead of `powersOfTau([G1],[G2])` and a `witness` that Ethereum's setup has
- Is it the same KZG impl? Why are those setups different?
- It is, it's KZG10
- Ok, so how do I parse this?
- Using info from [Vitalik's post](https://vitalik.ca/general/2022/03/14/trustedsetup.html)
- `powersOfTau` contains `G1` and `G2` elements that have a relationship between them; we use that relationship to track the integrity of contributions
- Similarly, `witness` is the actual proof of this integrity
- 
- Ok, so `[G1], VerifierKey` makes sense now. But what do I do with `VerifierKey`?
- For [KZG10 implementation in arkworks](https://github.com/arkworks-rs/poly-commit/blob/master/src/kzg10/mod.rs#L135-L136) I need both `powers_of_g` and `powers_of_g_gamma`. The former is just `G1Powers`. The latter is not available in Ethereum's KZG transcript
- This is because Ethereum's KZG setup uses MPC, so the "security gadget" used by verifier is different (G2 elements instead of G1 elements)
- What do I do here? Does that mean that I can't use Ethereum's KZG with arkworks implementation? Is there any math trick I could use here?
- Not sure if I'm understanding, but let's try:
- `powers_of_g_gamma` is `powers_of_g` exponentiated to another secret, taken from generator h (in G2)
- In Ethereum's ceremony, everyone takes turn to incorporate their secret into the `powers_of_gamma`
- 

## Other approaches
https://github.com/alxiong/crs