Source file pvss_secp256k1.ml

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open Secp256k1_group

module G : Pvss.CYCLIC_GROUP = struct
  module Z_m = struct
    include Group.Scalar

    let n = Group.order

    let ( + ) = Group.Scalar.add

    let ( * ) = Group.Scalar.mul

    let ( - ) = Group.Scalar.sub

    let ( = ) = Group.Scalar.equal

    let inv = Group.Scalar.inverse
  end

  include Group

  let name = "secp256k1"

  (* This pvss algorithm assumes the public keys of the participants receiving
     shares are based on g2, so we set g2 to Group.g to match regular Secp256k1
     public keys.
  *)
  let g1 = Group.h

  let g2 = Group.g

  (* We use a multiplicative notation in the pvss module, but
     secp256k1 usually uses an additive notation. *)
  let ( * ) = Group.(( + ))

  let pow x n = Group.mul n x

  let of_bits b = Option.catch (fun () -> Group.of_bits_exn b)
end

include Pvss.MakePvss (G)

let convert_encoding de1 de2 x =
  Data_encoding.Binary.of_bytes_exn
    de2
    (Data_encoding.Binary.to_bytes_exn de1 x)

let generate_keys ?(seed = Hacl.Rand.gen 32) () =
  let s =
    Secp256k1_group.Group.Scalar.of_bits_exn
      (Bigstring.of_bytes seed |> Bigstring.to_string)
  in
  let sk =
    convert_encoding Secp256k1_group.Group.Scalar.encoding Secret_key.encoding s
  in
  let pk = Secret_key.to_public_key sk in
  (pk, sk)