diff --git a/src/binary_formats.ml b/src/binary_formats.ml
index bb840af8..a750e089 100644
--- a/src/binary_formats.ml
+++ b/src/binary_formats.ml
@@ -364,7 +364,7 @@ module BlindingMasterSeed = MK_BASIC_32 ()
 
 (* Format used for to generate the signature on a request to withdraw
    coins from a reserve. *)
-module WithdrawRequestPs = struct
+module WithdrawRequestPS = struct
   (* Purpose is #TALER_SIGNATURE_WALLET_RESERVE_WITHDRAW *)
   type t = {
     (* Amount to withdraw, excluding fees, i.e.
@@ -432,7 +432,7 @@ module WithdrawRequestPs = struct
     |> sealr
 end
 
-module WithdrawConfirmationPs = struct
+module WithdrawConfirmationPS = struct
   (* Purpose is #TALER_SIGNATURE_EXCHANGE_CONFIRM_WITHDRAW.
      Signed by a `struct TALER_ExchangePrivateKeyP` using EdDSA. *)
   type t = {
@@ -451,15 +451,23 @@ module WithdrawConfirmationPs = struct
     noreveal_index: int32;
   }
 
-  let size = Purpose.size + HashPlanchetsP.size + int32_size
-  let purpose = Purpose.make ~size Taler_signatures.exchange_confirm_withdraw
+  (*let size = Purpose.size + HashPlanchetsP.size + int32_size*)
+
+  open Bin
 
   let bin =
-    let open Bin in
-    record (fun _urpose h_planchets noreveal_index ->
-        { h_planchets; noreveal_index })
-    |+ field Purpose.bin (Fun.const purpose)
-    |+ field HashPlanchetsP.bin (fun t -> t.h_planchets)
-    |+ field beint32 (fun t -> t.noreveal_index)
+    record (fun purpose h_planchets noreveal_index ->
+        (purpose, { h_planchets; noreveal_index }))
+    |+ field Purpose.bin (fun (purpose, _t) -> purpose)
+    |+ field HashPlanchetsP.bin (fun (_p, t) -> t.h_planchets)
+    |+ field beint32 (fun (_p, t) -> t.noreveal_index)
     |> sealr
+
+  let size =
+    match Size.of_value (Size.size_of bin) with
+    | Dynamic _ | Unknown -> Fmt.failwith "size_of failure: size is not Static"
+    | Static n -> n
+
+  let purpose = Purpose.make ~size Taler_signatures.exchange_confirm_withdraw
+  let bin = map bin (fun (_p, t) -> t) (fun t -> (purpose, t))
 end
diff --git a/src/json.ml b/src/json.ml
index c4a34de6..f800b83a 100644
--- a/src/json.ml
+++ b/src/json.ml
@@ -4,8 +4,8 @@ let encode_exn jsont v = Jsont_bytesrw.encode_string jsont v |> Result.get_ok
 let encode jsont v = Jsont_bytesrw.encode_string jsont v
 let decode jsont v = Jsont_bytesrw.decode_string jsont v
 
-module Error_detail = struct
-  open Error_detail
+module ErrorDetail = struct
+  open ErrorDetail
 
   let jsont =
     let make code hint = { code; hint } in
@@ -45,8 +45,8 @@ module Timestamp = struct
     |> Jsont.Object.finish
 end
 
-module Relative_time = struct
-  open Relative_time
+module RelativeTime = struct
+  open RelativeTime
 
   let number_or_forever_jsont =
     let forever =
@@ -87,8 +87,8 @@ module Eddsa = struct
   let signature_jsont = Jsont.string
 end
 
-module Rsa_denomination_key = struct
-  open Rsa_denomination_key
+module RsaDenominationKey = struct
+  open RsaDenominationKey
 
   let jsont =
     let make age_mask rsa_pub = { age_mask; rsa_pub } in
@@ -100,8 +100,8 @@ module Rsa_denomination_key = struct
     |> Jsont.Object.finish
 end
 
-module CS_denomination_key = struct
-  open CS_denomination_key
+module CSDenominationKey = struct
+  open CSDenominationKey
 
   let jsont =
     let make age_mask cs_pub = { age_mask; cs_pub } in
@@ -113,16 +113,16 @@ module CS_denomination_key = struct
     |> Jsont.Object.finish
 end
 
-module Denomination_key = struct
-  open Denomination_key
+module DenominationKey = struct
+  open DenominationKey
 
   let rsa v = Rsa v
   let cs v = CS v
 
   let jsont =
     let open Jsont.Object in
-    let rsa = Case.map "RSA" Rsa_denomination_key.jsont ~dec:rsa in
-    let cs = Case.map "CS" CS_denomination_key.jsont ~dec:cs in
+    let rsa = Case.map "RSA" RsaDenominationKey.jsont ~dec:rsa in
+    let cs = Case.map "CS" CSDenominationKey.jsont ~dec:cs in
     let enc_case = function
       | Rsa v -> Case.value rsa v
       | CS v -> Case.value cs v
@@ -133,8 +133,8 @@ module Denomination_key = struct
     |> finish
 end
 
-module Future_sign_key = struct
-  open Future_sign_key
+module FutureSignKey = struct
+  open FutureSignKey
 
   let jsont =
     (* TODO ppx? *)
diff --git a/src/mte.ml b/src/mte.ml
index 1b77f44b..8c013b47 100644
--- a/src/mte.ml
+++ b/src/mte.ml
@@ -14,10 +14,10 @@
     along with this program.  If not, see <https://www.gnu.org/licenses/>. *)
 
 let error_detail ?hint _status =
-  let open Types.Error_detail in
+  let open Types.ErrorDetail in
   let open Json in
   let code = -1 in
-  let s = encode_exn Error_detail.jsont { code; hint } in
+  let s = encode_exn ErrorDetail.jsont { code; hint } in
   s
 
 module Respond_with = struct
diff --git a/src/types.ml b/src/types.ml
index f4546537..d1f43f96 100644
--- a/src/types.ml
+++ b/src/types.ml
@@ -1,5 +1,5 @@
 (* https://docs.taler.net/core/api-common.html#tsref-type-ErrorDetail *)
-module Error_detail = struct
+module ErrorDetail = struct
   (* TODO GANA error codes
      https://git.gnunet.org/gana.git/tree/gnu-taler-error-codes/registry.rec *)
   type t = {
@@ -21,7 +21,7 @@ module Timestamp = struct
     | Never
 end
 
-module Relative_time = struct
+module RelativeTime = struct
   (* Duration in microseconds or "forever"
      to represent an infinite duration. Numeric
      values are capped at 2^53 - 1 inclusive. *)
@@ -147,19 +147,19 @@ module Rsa = struct
   let pub_to_string _pub = assert false
 end
 
-module Hash_code = struct
+module HashCode = struct
   (* 32-byte value representing a point on Curve25519. *)
   type cs25519Point = string
 end
 
-module Rsa_denomination_key = struct
+module RsaDenominationKey = struct
   type t = {
     age_mask: int;
     rsa_pub: string; (* Rsa.pub *)
   }
 end
 
-module CS_denomination_key = struct
+module CSDenominationKey = struct
   (* Clause Schnorr *)
   type t = {
     age_mask: int;
@@ -167,13 +167,13 @@ module CS_denomination_key = struct
   }
 end
 
-module Denomination_key = struct
+module DenominationKey = struct
   type t =
-    | Rsa of Rsa_denomination_key.t
-    | CS of CS_denomination_key.t
+    | Rsa of RsaDenominationKey.t
+    | CS of CSDenominationKey.t
 end
 
-module Future_sign_key = struct
+module FutureSignKey = struct
   type t = {
     (* The actual exchange's EdDSA signing public key *)
     key: Eddsa.pub;
diff --git a/test/dune b/test/dune
index 57d2e7e5..1eefa8ef 100644
--- a/test/dune
+++ b/test/dune
@@ -2,3 +2,10 @@
  (name test)
  (modules test)
  (libraries mte fmt))
+
+; TODO
+; cram test?
+; gcc -o a.out ./test/signatures.c && ./a.out > a.output
+; rm ./a.out
+; dune exec ./test/test.exe > b.output
+; cmp -l a.output b.output
diff --git a/test/signatures.c b/test/signatures.c
new file mode 100644
index 00000000..bcebe993
--- /dev/null
+++ b/test/signatures.c
@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <stdint.h>
+
+struct H64 {
+  uint8_t hash[64];
+};
+struct Hhh {
+  struct H64 hash;
+};
+struct Purpose {
+  uint32_t size;
+  uint32_t purpose;
+};
+
+struct PS {
+  struct Purpose purpose;
+  struct Hhh h;
+  uint32_t noreveal_index;
+};
+
+int main(void) {
+    struct Purpose purpose;
+    struct PS ps;
+
+    purpose.size = 3 * 4 + 64;
+    purpose.purpose = 1050;
+
+    struct Hhh h = {
+        .hash = {
+            .hash = {
+                1 , 2 , 3 , 4 , 5, 6, 7, 8,
+                9 , 10, 11, 12, 13, 14, 15, 16,
+                17, 18, 19, 20, 21, 22, 23, 24,
+                25, 26, 27, 28, 29, 30, 31, 32,
+                33, 34, 35, 36, 37, 38, 39, 40,
+                41, 42, 43, 44, 45, 46, 47, 48,
+                49, 50, 51, 52, 53, 54, 55, 56,
+                57, 58, 59, 60, 61, 62, 63, 64
+            }
+        }
+    };
+
+    uint32_t noreveal_index = 0;
+
+    ps.purpose = purpose;
+    ps.h = h;
+    ps.noreveal_index = noreveal_index;
+
+
+    fwrite(&ps, sizeof(ps), 1, stdout);
+
+    // printf("\n");
+
+    return 0;
+}
diff --git a/test/test.ml b/test/test.ml
index 0d8d4ed2..8f233513 100644
--- a/test/test.ml
+++ b/test/test.ml
@@ -18,9 +18,9 @@ let () =
   check_bad Timestamp.jsont {|{"t_s": "123456780"}|};
   check_bad Timestamp.jsont {|{"t_s": "agagou"}|};
 
-  check Denomination_key.jsont
+  check DenominationKey.jsont
     {|{"cipher": "RSA", "age_mask": 18, "rsa_pub": "agagouh"}|};
-  check Denomination_key.jsont
+  check DenominationKey.jsont
     {|{"cipher": "CS", "age_mask": 18, "cs_pub": "ouhagag"}|};
   ()
 
@@ -73,10 +73,15 @@ let () =
   ()
 
 let () =
-  let open Binary_formats.WithdrawConfirmationPs in
-  let str64 = String.make 64 '0' in
+  let open Binary_formats.WithdrawConfirmationPS in
+  let str64 = String.init 64 (fun i -> Char.unsafe_chr (i + 1)) in
   let dummy_t = { h_planchets= { v= { v= str64 } }; noreveal_index= 0_l } in
   let size' = Bin.size_of_value bin dummy_t |> Option.get in
   assert (size = size');
   assert (size = 76);
+
+  (* for cmp test with signatures.c output *)
+  let raw_str = Bin.to_string bin dummy_t in
+  Printf.printf "%s" raw_str;
+
   ()