From 1419ac7da73a71fb5c202f4232fa501775614789 Mon Sep 17 00:00:00 2001
From: swrup <swrup@protonmail.com>
Date: Sat, 18 Oct 2025 17:03:38 +0200
Subject: [PATCH]

---
 src/binary_formats.ml | 67 ++++++++++++++++++-------------------------
 src/types.ml          | 10 ++-----
 2 files changed, 31 insertions(+), 46 deletions(-)

diff --git a/src/binary_formats.ml b/src/binary_formats.ml
index 3faa3403..9541553c 100644
--- a/src/binary_formats.ml
+++ b/src/binary_formats.ml
@@ -242,27 +242,16 @@ module Taler_signatures = Include.Taler_signatures
 
 (* -- Cryptographic primitives -- *)
 
-(* GNUNET_CRYPTO format *)
-module GNUNET_RsaPublicKey = struct
-  (* libgnuutil format:
-     https://docs.gnunet.org/doxygen/d9/dbe/structGNUNET__CRYPTO__RsaPublicKeyHeaderP.html
-     https://docs.gnunet.org/doxygen/d6/d70/group__libgnunetutil.html#ga9c99a81e8cd649c1c925d23211a0738f
-     https://www.gnupg.org/documentation/manuals/gcrypt/MPI-formats.html
-
-    format:
-     - rsa header
-     - modulus
-     - public_exponent
+module RsaPublicKey = struct
+  (* https://www.gnupg.org/documentation/manuals/gcrypt/MPI-formats.html
+     format:
+      - uint16_be: n size
+      - uint16_be: e size
+      - n
+      - e
 
     integer in big-endian format (MSB first).
-    Leading zeroes are stripped unless they are required to keep a value positive.
-  *)
-  type t = {
-    n_len: int;
-    e_len: int;
-    n: Z.t;
-    e: Z.t;
-  }
+    Leading zeroes are stripped unless they are required to keep a value positive. *)
 
   let rev_string len s = String.init len (fun i -> s.[len - 1 - i])
 
@@ -271,10 +260,9 @@ module GNUNET_RsaPublicKey = struct
   let z_of_bits_be src pos len =
     String.sub src pos len |> rev_string len |> Z.of_bits
 
-  let of_pub ({ n; e } : Mirage_crypto_pk.Rsa.pub) =
-    { n_len= Z.size n; e_len= Z.size e; n; e }
-
-  let to_octets { n_len; e_len; n; e } =
+  let to_octets ({ n; e } : Mirage_crypto_pk.Rsa.pub) =
+    let n_len = Z.size n in
+    let e_len = Z.size e in
     let len = 4 + n_len + e_len in
     let b = Bytes.make len '\x00' in
     Bytes.set_uint16_be b 0 n_len;
@@ -285,27 +273,28 @@ module GNUNET_RsaPublicKey = struct
     Bytes.blit_string e 0 b (4 + n_len) e_len;
     Bytes.unsafe_to_string b
 
-  let of_octets s =
-    let error = Error "GNUNET_RsaPublicKey.of_octets: invalid data" in
-    let len = String.length s in
-    match len >= 4 with
-    | false -> error
-    | true -> (
-        let n_len = String.get_uint16_be s 0 in
-        let e_len = String.get_uint16_be s 2 in
-        match len = n_len + e_len + 4 with
-        | false -> error
-        | true ->
-            let n = z_of_bits_be s 4 n_len in
-            let e = z_of_bits_be s (4 + n_len) e_len in
-            Ok { n_len; e_len; n; e })
+  let of_octets =
+    let check = function
+      | false -> Error "RsaPublicKey.of_octets: invalid data"
+      | true -> Ok ()
+    in
+    fun s ->
+      let open Syntax in
+      let len = String.length s in
+      let* () = check (len >= 4) in
+      let n_len = String.get_uint16_be s 0 in
+      let e_len = String.get_uint16_be s 2 in
+      let* () = check (len = n_len + e_len + 4) in
+      let n = z_of_bits_be s 4 n_len in
+      let e = z_of_bits_be s (4 + n_len) e_len in
+      Mirage_crypto_pk.Rsa.pub ~n ~e |> unwrap_err_msg
 end
 
 module DenominationHash = MK_SRC_HASH_32 (struct
   type src = Mirage_crypto_pk.Rsa.pub
 
-  let to_octets pub =
-    GNUNET_RsaPublicKey.of_pub pub |> GNUNET_RsaPublicKey.to_octets
+  (* function to convert src type to a string for hashing *)
+  let to_octets = RsaPublicKey.to_octets
 end)
 
 module ExchangePublicKeyP = struct
diff --git a/src/types.ml b/src/types.ml
index 76269e74..0df429f6 100644
--- a/src/types.ml
+++ b/src/types.ml
@@ -132,17 +132,13 @@ end = struct
 end
 
 module RsaPublicKey = struct
-  type t = Mirage_crypto_pk.Rsa.pub
+  open Binary_formats.RsaPublicKey
 
-  let to_octets ({ n; e } : Mirage_crypto_pk.Rsa.pub) =
-    let open Binary_formats.GNUNET_RsaPublicKey in
-    let v = { n_len= Z.size n; e_len= Z.size e; n; e } in
-    let s = to_octets v in
-    s
+  type t = Mirage_crypto_pk.Rsa.pub
 
   let of_b32 s =
     let open Syntax in
-    let open Binary_formats.GNUNET_RsaPublicKey in
+    let open Binary_formats.RsaPublicKey in
     let* s = B32.decode s in
     let* v = of_octets s in
     let+ v = Mirage_crypto_pk.Rsa.pub ~n:v.n ~e:v.e |> unwrap_err_msg in