Source file pairing.ml

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(* Copyright (c) 2020-2021 Danny Willems <be.danny.willems@gmail.com>        *)
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exception FailToComputeFinalExponentiation of Fq12.t

module Stubs = struct
  external miller_loop : Fq12.t -> G2.Stubs.affine -> G1.Stubs.affine -> int
    = "caml_blst_miller_loop_stubs"

  external miller_loop_list : Fq12.t -> (G1.t * G2.t) array -> int -> int
    = "caml_blst_miller_loop_list_stubs"

  external final_exponentiation : Fq12.t -> Gt.t -> int
    = "caml_blst_final_exponentiation_stubs"
end

let miller_loop_simple g1 g2 =
  let buffer = Fq12.Stubs.allocate_fq12 () in
  let g1_affine = G1.Stubs.allocate_g1_affine () in
  let g2_affine = G2.Stubs.allocate_g2_affine () in
  ignore @@ G1.Stubs.to_affine g1_affine g1 ;
  ignore @@ G2.Stubs.to_affine g2_affine g2 ;
  ignore @@ Stubs.miller_loop buffer g2_affine g1_affine ;
  buffer

let miller_loop l =
  let out = Fq12.Stubs.allocate_fq12 () in
  let l = Array.of_list l in
  let length = Array.length l in
  ignore @@ Stubs.miller_loop_list out l length ;
  out

let final_exponentiation_opt x =
  if Fq12.is_zero x then None
  else
    let buffer = Fq12.Stubs.allocate_fq12 () in
    ignore @@ Stubs.final_exponentiation buffer x ;
    Some buffer

let final_exponentiation_exn x =
  if Fq12.is_zero x then raise (FailToComputeFinalExponentiation x)
  else
    let buffer = Fq12.Stubs.allocate_fq12 () in
    ignore @@ Stubs.final_exponentiation buffer x ;
    buffer

let pairing g1 g2 =
  let ml = miller_loop_simple g1 g2 in
  final_exponentiation_exn ml

let pairing_check points =
  let res_opt = miller_loop points |> final_exponentiation_opt in
  match res_opt with None -> false | Some res -> Gt.is_zero res