Revision 9b9eabddd2481575f85443267760777f9c62d808 authored by Lucas Randazzo on 27 February 2024, 16:41:35 UTC, committed by Marge Bot on 06 March 2024, 12:34:23 UTC
1 parent 83d289c
srs.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"),*)
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(* 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. *)
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(*****************************************************************************)
(** Formats used for Srs:
- the disk format uses compressed affine coordinates to save space
- the memory format uses uncompressed affine coordiantes, because it's
required by the pippenger API
- the interface and memory representation of an Srs is as carray of affine
elements (type G.affine) because they are however the interface that is
exposed uses jacobian format (the type G.t). *)
(* The Elt signature is extended with pippenger. *)
module type GElt_sig = sig
module G : Bls12_381.CURVE
include Carray.Elt_sig with type t = G.affine
(** [uncompress res bs n] reads [n] bytes from [bs] and uncompresses
them into an affine point in [res]. Returns 0 if successful. *)
val uncompress : G.affine -> bytes -> int
(* This function is already bound in Bls12-381 but not exposed. *)
(** [pippenger res srs poly offset len] writes in [res] the
multiexponentiation of [srs] with the polynomial [poly] starting at
[offset] and for [len] elements. Returns 0 if successful. *)
val pippenger : G.t -> Bigstringaf.t -> Polynomial.t -> int -> int -> int
end
module type S = sig
type polynomial
type t [@@deriving repr]
type elt
val empty : t
(** [get srs i] returns the [i]-th element of [srs] *)
val get : t -> int -> elt
(** Returns the pippenger ctxt size, i.e. the number of elements the context
is supposed to be called with *)
val size : t -> int
val of_bigstring :
?len:int ->
Bigstringaf.t ->
(t, [> `End_of_file of string | `Invalid_point of int]) result
(** [of_bigstring ~len bs] reads [len] points of G in affine
compressed format from [bs] and returns a Srs. If [len] is omitted the
whole bs is read.
The bigstring can be loaded from a file with:
{[
let bigstring_of_file filename =
let fd = Unix.openfile filename [ Unix.O_RDONLY ] 0o440 in
Bigarray.array1_of_genarray
@@ Unix.map_file fd Bigarray.char Bigarray.c_layout false
[| (* [-1] means read the whole file *) -1 |]
in
Srs_g1.of_bigstring
(bigstring_of_file ("srs_zcash_g1_21"))
(1 lsl 5)
]}
or with Lwt:
{[
let bigstring_of_file filename =
let fd = Unix.openfile filename [ Unix.O_RDONLY ] 0o440 in
Lwt_bytes.map_file ~fd ~shared:false ()
in
]} *)
val generate_insecure : int -> Bls12_381.Fr.t -> t
(** [pippenger ctxt poly] computes the multiscalar exponentiation using the
SRS saved in the context and the coefficients of the given polynomial *)
val pippenger : ?offset:int -> ?len:int -> t -> polynomial -> elt
(* TODO just for pack *)
val to_array : ?len:int -> t -> elt array
val of_array : elt array -> t
end
module Make (Elt : GElt_sig) = struct
module G = Elt.G
module Carray = Carray.Make (Elt)
type polynomial = Polynomial.Polynomial_unsafe.t
type t = Carray.t [@@deriving repr]
type elt = G.t
let size = Carray.length
let get p i = Carray.get p i |> G.jacobian_of_affine
let to_array ?len data =
Carray.to_array ?len data |> Array.map G.jacobian_of_affine
let of_array caml_array =
Carray.of_array (Array.map G.affine_of_jacobian caml_array)
let empty = Carray.empty
let generate_insecure d x =
let xi = ref G.one in
Array.init d (fun _ ->
let res = !xi in
xi := G.mul !xi x ;
res)
|> of_array
let of_bigstring ?len bs =
let size_compressed = Elt.size / 2 in
let n =
Option.value ~default:(Bigstringaf.length bs / size_compressed) len
in
let data = Carray.allocate n in
let buf = Bytes.create size_compressed in
let point = Elt.allocate () in
let ( let* ) = Stdlib.Result.bind in
let rec loop i =
if i = n then Ok ()
else
let* () =
try
Ok
(Bigstringaf.blit_to_bytes
bs
~src_off:(i * size_compressed)
buf
~dst_off:0
~len:size_compressed)
with _ ->
Error
(`End_of_file
(Format.sprintf "found only %d elements of the required %d" i n))
in
let code = Elt.uncompress point buf in
let* () = if code <> 0 then Error (`Invalid_point i) else Ok () in
Carray.set data point i ;
loop (i + 1)
in
let* () = loop 0 in
Ok data
let pippenger ?(offset = 0) ?len srs poly =
if Polynomial.is_zero poly then G.zero
else
let poly_length = Polynomial.degree poly + 1 in
let len = Option.value ~default:(poly_length - offset) len in
if
len <= 0 || offset < 0
|| poly_length - offset < len
|| size srs - offset < len
then
raise
@@ Invalid_argument
(Format.sprintf
"pippenger: invalid len %d or offset %d for size %d"
len
offset
poly_length) ;
let res = G.(copy zero) in
let return_code =
Elt.pippenger res (Carray.to_bigstring srs) poly offset len
in
assert (return_code = 0) ;
res
end
module Elt_g1 = struct
module G = Bls12_381.G1
type t = G.affine
let size = G.size_in_bytes
let allocate () = G.(affine_of_jacobian zero)
let zero = G.(affine_of_jacobian zero)
let eq a b = G.eq (G.jacobian_of_affine a) (G.jacobian_of_affine b)
external uncompress : t -> bytes -> int = "caml_blst_p1_uncompress_stubs"
[@@noalloc]
external pippenger : G.t -> Bigstringaf.t -> Polynomial.t -> int -> int -> int
= "caml_bls12_381_polynomial_srs_g1_pippenger_stubs"
[@@noalloc]
end
module Elt_g2 = struct
module G = Bls12_381.G2
type t = G.affine
let size = G.size_in_bytes
let allocate () = G.(affine_of_jacobian zero)
let zero = G.(affine_of_jacobian zero)
let eq a b = G.eq (G.jacobian_of_affine a) (G.jacobian_of_affine b)
external uncompress : G.affine -> bytes -> int
= "caml_blst_p2_uncompress_stubs"
[@@noalloc]
external pippenger : G.t -> Bigstringaf.t -> Polynomial.t -> int -> int -> int
= "caml_bls12_381_polynomial_srs_g2_pippenger_stubs"
[@@noalloc]
end
module Srs_g1 :
S with type elt = Bls12_381.G1.t and type polynomial = Polynomial.t =
Make (Elt_g1)
module Srs_g2 :
S with type elt = Bls12_381.G2.t and type polynomial = Polynomial.t =
Make (Elt_g2)
module Checks = struct
open Bls12_381
let equality g1s g2s =
let g1 = Srs_g1.get g1s 0 in
let g2 = Srs_g2.get g2s 0 in
let size = min (Srs_g1.size g1s) (Srs_g2.size g2s) in
for i = 0 to size - 1 do
let g1i = Srs_g1.get g1s i in
let g2i = Srs_g2.get g2s i in
let gt1 = Pairing.pairing g1i g2 in
let gt2 = Pairing.pairing g1 g2i in
assert (GT.eq gt1 gt2)
done
let incrementation_g1 g1s g2s =
let g2 = Srs_g2.get g2s 0 in
let g2x = Srs_g2.get g2s 1 in
for i = 0 to Srs_g1.size g1s - 2 do
let g1i = Srs_g1.get g1s i in
let g1iplus = Srs_g1.get g1s (i + 1) in
let gt1 = Pairing.pairing g1i g2x in
let gt2 = Pairing.pairing g1iplus g2 in
assert (GT.eq gt1 gt2)
done
let incrementation_g2 g1s g2s =
let g1 = Srs_g1.get g1s 0 in
let g1x = Srs_g1.get g1s 1 in
for i = 0 to Srs_g2.size g2s - 2 do
let g2i = Srs_g2.get g2s i in
let g2iplus = Srs_g2.get g2s (i + 1) in
let gt1 = Pairing.pairing g1x g2i in
let gt2 = Pairing.pairing g1 g2iplus in
assert (GT.eq gt1 gt2)
done
let pairings (g1s, g2s) =
equality g1s g2s ;
incrementation_g1 g1s g2s ;
incrementation_g2 g1s g2s
end
module Srs = struct
module Srs_g1 = Srs_g1
module Srs_g2 = Srs_g2
type t = Srs_g1.t * Srs_g2.t
let generate_insecure log_g1 log_g2 =
let x = Bls12_381.Fr.random () in
( Srs_g1.generate_insecure (1 lsl log_g1) x,
Srs_g2.generate_insecure (1 lsl log_g2) x )
let check = Checks.pairings
end
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