Source file g1.ml

(*****************************************************************************)
(*                                                                           *)
(* Copyright (c) 2020-2021 Danny Willems <be.danny.willems@gmail.com>        *)
(*                                                                           *)
(* Permission is hereby granted, free of charge, to any person obtaining a   *)
(* copy of this software and associated documentation files (the "Software"),*)
(* to deal in the Software without restriction, including without limitation *)
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(* and/or sell copies of the Software, and to permit persons to whom the     *)
(* Software is furnished to do so, subject to the following conditions:      *)
(*                                                                           *)
(* The above copyright notice and this permission notice shall be included   *)
(* in all copies or substantial portions of the Software.                    *)
(*                                                                           *)
(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
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(* DEALINGS IN THE SOFTWARE.                                                 *)
(*                                                                           *)
(*****************************************************************************)

module type RAW = sig
  include Elliptic_curve_sig.RAW_BASE

  val build_from_components : Bytes.t -> Bytes.t -> Bytes.t option
end

module type T = sig
  include Elliptic_curve_sig.T

  (** Create a point from the coordinates. If the point is not on the curve,
    [None] is return. The points must be given modulo the order of Fq. To create
    the point at infinity, use [zero ()] *)
  val of_z_opt : x:Z.t -> y:Z.t -> t option
end

module Make (Scalar : Fr.T) (Stubs : RAW) : T with module Scalar = Scalar =
struct
  include Elliptic_curve_sig.Make (Scalar) (Stubs)

  let of_z_opt ~x ~y =
    let x_bytes = Bytes.make 48 '\000' in
    let x = Bytes.of_string (Z.to_bits x) in
    Bytes.blit x 0 x_bytes 0 (min (Bytes.length x) 48) ;
    let y_bytes = Bytes.make 48 '\000' in
    let y = Bytes.of_string (Z.to_bits y) in
    Bytes.blit y 0 y_bytes 0 (min (Bytes.length y) 48) ;
    let res = Stubs.build_from_components x_bytes y_bytes in
    match res with None -> None | Some res -> Some (of_bytes_exn res)
end