Revision d8f4b9d21f954c3fa150d8ad8f715375e15ef532 authored by KOBAYASHI Kazuhiro on 20 April 2023, 08:01:02 UTC, committed by Marge Bot on 13 June 2023, 11:56:25 UTC
1 parent 98fbc20
fr_carray.ml
(*****************************************************************************)
(* *)
(* MIT License *)
(* Copyright (c) 2022 Nomadic Labs <contact@nomadic-labs.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 *)
(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
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(* DEALINGS IN THE SOFTWARE. *)
(* *)
(*****************************************************************************)
module Scalar = Bls12_381.Fr
module Elt = struct
type t = Scalar.t
let size = Scalar.size_in_bytes
let zero = Scalar.zero
let allocate () = Scalar.(copy zero)
let eq = Scalar.eq
end
include Carray.Make (Elt)
(* Generator of the multiplicative group Fr^* *)
let generator = Scalar.of_int 7
(* Samples a primitive [n]-th root of unity. *)
let primitive_root_of_unity n =
let n = Z.of_int n in
let multiplicative_group_order = Z.(Scalar.order - one) in
if not (Z.divisible multiplicative_group_order n) then
raise
(Invalid_argument
(Format.sprintf
"There do not exist %s-th roots of unity"
(Z.to_string n)))
else
let exponent = Z.divexact multiplicative_group_order n in
Scalar.pow generator exponent
(* Samples a 2^i-th root of unity, assuming that it exists *)
let primitive_root_of_unity_power_of_two ~log =
primitive_root_of_unity (1 lsl log)
let build_array init next len =
let xi = ref init in
Array.init len (fun _ ->
let i = !xi in
xi := next !xi ;
i)
(* TODO return carray instead of array ? *)
(* computes [| 1; x; x²; x³; ...; xᵈ⁻¹ |] *)
let powers d x = build_array Scalar.one Scalar.(mul x) d
let build_domain n = powers n (primitive_root_of_unity n)
let build_domain_power_of_two ~log =
let g = primitive_root_of_unity_power_of_two ~log in
powers (1 lsl log) g
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