diff --git a/src/api.ml b/src/api.ml
index f6dd4427..47d2156e 100644
--- a/src/api.ml
+++ b/src/api.ml
@@ -90,40 +90,42 @@ module RsaDenominationKey = struct
     |> Jsont.Object.finish
 end
 
-(* not acctually implemented *)
+(* ! Clause Schnorr cipher is not supported *)
 module CSDenominationKey = struct
-  (* Clause Schnorr *)
   type t = {
     age_mask: int;
-    cs_pub: string;
+    cs_pub: B32.t;
   }
 
+  (* TODO B32.jsont *)
+  let b32_jsont = Jsont.of_of_string ~kind:"B32" B32.decode ~enc:B32.encode
+
   let jsont =
     let make age_mask cs_pub = { age_mask; cs_pub } in
     let age_mask v = v.age_mask in
     let cs_pub v = v.cs_pub in
     Jsont.Object.map ~kind:"CSDenominationKey" make
     |> Jsont.Object.mem "age_mask" Jsont.int ~enc:age_mask
-    |> Jsont.Object.mem "cs_pub" Jsont.string ~enc:cs_pub
+    |> Jsont.Object.mem "cs_pub" b32_jsont ~enc:cs_pub
     |> Jsont.Object.finish
 end
 
 module DenominationKey = struct
-  type t =
-    | Rsa of RsaDenominationKey.t
-    | CS of CSDenominationKey.t
+  type t = Rsa of RsaDenominationKey.t
+  (*| CS of CSDenominationKey.t*)
 
-  let rsa v = Rsa v
-  let cs v = CS v
+  let to_octets = function Rsa denom -> RsaPublicKey.to_octets denom.rsa_pub
+
+  let of_cs _v =
+    Jsont.Error.msg Jsont.Meta.none "CSDenominationKey are not supported"
+
+  let of_rsa v = Rsa v
 
   let jsont =
     let open Jsont.Object 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
-    in
+    let rsa = Case.map "RSA" RsaDenominationKey.jsont ~dec:of_rsa in
+    let cs = Case.map "CS" CSDenominationKey.jsont ~dec:of_cs in
+    let enc_case = function Rsa v -> Case.value rsa v in
     let cases = Case.[ make rsa; make cs ] in
     map ~kind:"DenominationKey" Fun.id
     |> case_mem "cipher" Jsont.string ~enc:Fun.id ~enc_case cases
@@ -171,7 +173,7 @@ module FutureDenom = struct
     fee_deposit: Amount.t;
     fee_refresh: Amount.t;
     fee_refund: Amount.t;
-    denom_secmod_sig: EddsaSignature.t;
+    denom_secmod_sig: Bin_signature.DenominationKeyAnnouncementPS.Sig.t;
   }
 
   let jsont =
@@ -218,7 +220,9 @@ module FutureDenom = struct
     |> mem "fee_deposit" Amount.jsont ~enc:fee_deposit
     |> mem "fee_refresh" Amount.jsont ~enc:fee_refresh
     |> mem "fee_refund" Amount.jsont ~enc:fee_refund
-    |> mem "denom_secmod_sig" EddsaSignature.jsont ~enc:denom_secmod_sig
+    |> mem "denom_secmod_sig"
+         Bin_signature.DenominationKeyAnnouncementPS.Sig.jsont
+         ~enc:denom_secmod_sig
     |> finish
 end
 
diff --git a/src/bin_signature.ml b/src/bin_signature.ml
index 84fdbac4..f7d30051 100644
--- a/src/bin_signature.ml
+++ b/src/bin_signature.ml
@@ -88,7 +88,7 @@ module DenominationKeyAnnouncementPS = struct
   (* TODO taler_signatures purpose
      we use TALER_SIGNATURE_SM_RSA_DENOMINATION_KEY instead here *)
   (* purpose.purpose = TALER_SIGNATURE_SM_DENOMINATION_KEY *)
-  type t = {
+  type r = {
     h_denom_pub: DenominationHash.t;
     h_section_name: Hash_64_cstr.t;
     anchor_time: TimeAbsoluteNBO.t;
@@ -107,6 +107,24 @@ module DenominationKeyAnnouncementPS = struct
     |+ field TimeAbsoluteNBO.bin (fun t -> t.anchor_time)
     |+ field TimeRelativeNBO.bin (fun t -> t.duration_withdraw)
     |> sealr
+
+  module type SIG = sig
+    type t
+
+    val sign : (string -> string) -> r -> t
+    val verify : (string -> msg:string -> bool) -> t -> r -> bool
+    val jsont : t Jsont.t
+  end
+
+  module Sig : SIG = struct
+    type t = string
+
+    let sign f r = f @@ Bin.to_string bin r
+    let verify f s r = f s ~msg:(Bin.to_string bin r)
+
+    (* TODO B32.jsont, for others types too *)
+    let jsont = Jsont.string
+  end
 end
 
 module SigningKeyAnnouncementPS = struct
diff --git a/src/crypto.ml b/src/crypto.ml
index 249d051e..8fda65f3 100644
--- a/src/crypto.ml
+++ b/src/crypto.ml
@@ -52,6 +52,7 @@ module EddsaSignature : sig
   type t
 
   val sign : key:Mirage_crypto_ec.Ed25519.priv -> string -> t
+  val sign_as_string : key:Mirage_crypto_ec.Ed25519.priv -> string -> string
   val of_b32 : string -> (t, string) result
   val to_b32 : t -> string
   val to_octets : t -> string
@@ -81,6 +82,8 @@ end = struct
     (* mirage_crypto: "The result is the concatenation of r and s, as specified in RFC 8032." *)
     Mirage_crypto_ec.Ed25519.sign ~key s
 
+  let sign_as_string ~key s = sign ~key s
+
   let check_size t =
     match String.length t = 64 with
     | false -> Error "EddsaSignature: invalid string length"
diff --git a/src/management.ml b/src/management.ml
index e1e21617..1aff93fe 100644
--- a/src/management.ml
+++ b/src/management.ml
@@ -21,19 +21,18 @@ let mk_future_denom denom_key_signf
      } :
       Denomination.t) =
   let denom_pub =
-    DenominationKey.Rsa RsaDenominationKey.{ age_mask; rsa_pub= pub }
+    DenominationKey.of_rsa RsaDenominationKey.{ age_mask; rsa_pub= pub }
   in
   let denom_secmod_sig =
-    let open Bin_type in
     let open Bin_signature.DenominationKeyAnnouncementPS in
     let h_denom_pub = h_pub in
-    let h_section_name = Hash_64_cstr.hash section_name in
+    let h_section_name = Bin_type.Hash_64_cstr.hash section_name in
     let anchor_time = stamp_start in
     let duration_withdraw =
       Timestamp.diff stamp_start stamp_expire_withdraw |> Timestamp.of_span_exn
     in
-    let ps = { h_denom_pub; h_section_name; anchor_time; duration_withdraw } in
-    ps |> Bin.to_string bin |> denom_key_signf
+    Sig.sign denom_key_signf
+      { h_denom_pub; h_section_name; anchor_time; duration_withdraw }
   in
   FutureDenom.
     {
@@ -61,8 +60,9 @@ let mk_future_signkey signkey_signf
     let duration =
       Timestamp.diff stamp_start stamp_expire |> Timestamp.of_span_exn
     in
-    let ps = { exchange_pub; anchor_time; duration } in
-    ps |> Bin.to_string bin |> signkey_signf
+    { exchange_pub; anchor_time; duration }
+    |> Bin.to_string bin
+    |> signkey_signf
   in
   FutureSignKey.
     { key= pub; stamp_start; stamp_expire; stamp_end; signkey_secmod_sig }
@@ -74,7 +74,8 @@ let mk_future_keys_response (secmod_signkey : Secmod_signkey.t)
     |> List.filter (fun k -> Option.is_none k.Denomination.master_sig)
     |> List.map (fun denom ->
         let signf s =
-          Crypto.EddsaSignature.sign ~key:secmod_denom.sm_key.Signkey.priv s
+          Crypto.EddsaSignature.sign_as_string
+            ~key:secmod_denom.sm_key.Signkey.priv s
         in
         mk_future_denom signf denom)
   in
diff --git a/test/test.ml b/test/test.ml
index 4e9efd4d..4377e198 100644
--- a/test/test.ml
+++ b/test/test.ml
@@ -15,11 +15,13 @@ let () =
   in
   ()
 
+let get_ok = function Error e -> failwith e | Ok v -> v
+
 let () =
   let open Api in
   let check jsont s =
-    let encode v = encode jsont v |> Result.get_ok in
-    let decode v = decode jsont v |> Result.get_ok in
+    let encode v = encode jsont v |> get_ok in
+    let decode v = decode jsont v |> get_ok in
     let ts = decode s in
     let s' = encode ts in
     let ts' = decode s' in
@@ -35,13 +37,14 @@ let () =
   check_bad Timestamp.jsont {|{"t_s": "123456780"}|};
   check_bad Timestamp.jsont {|{"t_s": "agagou"}|};
 
-  (* TODO use a valid rsa_pub value *)
-  (*
-  check DenominationKey.jsont
-    {|{"cipher": "RSA", "age_mask": 18, "rsa_pub": "agagouh"}|};
-  check DenominationKey.jsont
+  (* CS not implemented *)
+  check_bad DenominationKey.jsont
     {|{"cipher": "CS", "age_mask": 18, "cs_pub": "ouhagag"}|};
-    *)
+
+  (* TODO test with a valid rsa_pub value *)
+  (* TODO handle "rsa pub_of_octets failure" correctly *)
+  (* check_bad DenominationKey.jsont
+    {|{"cipher": "RSA", "age_mask": 18, "rsa_pub": "agagouh"}|}; *)
   ()
 
 let () =
diff --git a/tools/offline_bin.ml b/tools/offline_bin.ml
index 016667d0..1919706d 100644
--- a/tools/offline_bin.ml
+++ b/tools/offline_bin.ml
@@ -19,20 +19,12 @@ let denom_signature ~master_key
         (* TODO check sigs *)
         denom_secmod_sig= _;
       } =
-  let pub_octets =
-    let denom_pub =
-      match denom_pub with
-      | Rsa v -> v
-      | CS _ -> Fmt.failwith "CS key types are not supported."
-    in
-    let pub = denom_pub.RsaDenominationKey.rsa_pub in
-    RsaPublicKey.to_octets pub
-  in
-  let h_denom_pub = HashCode.hash pub_octets in
+  let octets = DenominationKey.to_octets denom_pub in
+  let h_denom_pub = HashCode.hash octets in
   let master_sig =
     let open Bin_signature.DenominationKeyValidityPS in
     let master = EddsaPrivateKey.(pub_of_priv master_key) in
-    let denom_hash = DenominationHash.hash pub_octets in
+    let denom_hash = DenominationHash.hash octets in
     {
       master;
       start= stamp_start;