diff --git a/src/secmod_eddsa.ml b/src/secmod_eddsa.ml
index 7db483e0..91d00f46 100644
--- a/src/secmod_eddsa.ml
+++ b/src/secmod_eddsa.ml
@@ -1,8 +1,8 @@
 open Syntax
 open Crypto
-open Mirage_crypto_ec
-open Config.Exchange_secmod_eddsa
 open Time
+open Mirage_crypto_ec
+module Cfg = Config.Exchange_secmod_eddsa
 
 type priv = Ed25519.priv
 type pub = Ed25519.pub
@@ -36,12 +36,12 @@ let time_abs_to_string abs =
   |> string_of_int
 
 let read_key fname =
-  let fpath = Fpath.(v key_dir / fname) in
+  let fpath = Fpath.(v Cfg.key_dir / fname) in
   let* data = Bos.OS.File.read fpath |> unwrap_err_msg in
   EddsaPrivateKey.of_octets data
 
 let write_eddsa fname priv =
-  let fpath = Fpath.(v key_dir / fname) in
+  let fpath = Fpath.(v Cfg.key_dir / fname) in
   let data = EddsaPrivateKey.to_octets priv in
   Bos.OS.File.write fpath data |> unwrap_err_msg
 
@@ -55,12 +55,12 @@ let split_in_periodes ~start ~end_ =
   (* no overlap on first periode
      this is to not generate a key valid in the past *)
   let t1 = start in
-  let t2 = Absolute.add start duration in
+  let t2 = Absolute.add start Cfg.duration in
   let acc = [ (t1, t2) ] in
   let start = t2 in
   let rec go acc start end_ =
-    let t1 = Absolute.sub start overlap_duration in
-    let t2 = Absolute.add start duration in
+    let t1 = Absolute.sub start Cfg.overlap_duration in
+    let t2 = Absolute.add start Cfg.duration in
     if t2 > end_ then acc else go ((t1, t2) :: acc) t2 end_
   in
   go acc start end_
@@ -73,9 +73,9 @@ let gen_additional_keys_until_lookahead ~now l =
     let l_rev = List.rev l in
     match l_rev with
     | [] -> now
-    | hd :: _ -> Absolute.sub hd.t2 overlap_duration
+    | hd :: _ -> Absolute.sub hd.t2 Cfg.overlap_duration
   in
-  let end_ = Absolute.add now lookahead_sign in
+  let end_ = Absolute.add now Cfg.lookahead_sign in
   let periodes = split_in_periodes ~start ~end_ in
   let new_keys =
     List.map
@@ -108,7 +108,7 @@ let purge_outdated ~now l =
 
 let load_key fpath =
   let fname = Fpath.filename fpath in
-  if fname = sm_priv_key then Ok None
+  if fname = Cfg.sm_priv_key then Ok None
   else
     match String.split_on_char '-' fname with
     | [] -> Fmt.failwith "not possible"
@@ -122,7 +122,7 @@ let load_key fpath =
     | _ -> Ok None
 
 let load () =
-  let dir = Fpath.v key_dir in
+  let dir = Fpath.v Cfg.key_dir in
   let* b = Bos.OS.Dir.create ~mode:0o700 dir |> unwrap_err_msg in
   if b then
     Logs.info (fun m -> m "secmod_eddsa: created directory `%a`" Fpath.pp dir);
@@ -134,7 +134,7 @@ let load () =
   match keys with
   | [] -> Ok None
   | _l ->
-      let* sm_key_priv = read_key sm_priv_key in
+      let* sm_key_priv = read_key Cfg.sm_priv_key in
       let sm_key_pub = EddsaPrivateKey.pub_of_priv sm_key_priv in
       Ok (Some { sm_key_priv; sm_key_pub; keys })
 
@@ -145,7 +145,7 @@ let init () =
     | Some t -> Ok t
     | None ->
         let sm_key_priv, sm_key_pub = Mirage_crypto_ec.Ed25519.generate () in
-        let* () = write_eddsa sm_priv_key sm_key_priv in
+        let* () = write_eddsa Cfg.sm_priv_key sm_key_priv in
         Ok { sm_key_priv; sm_key_pub; keys= [] }
   in
   let now = Absolute.of_ptime (Ptime_clock.now ()) in
@@ -163,15 +163,25 @@ let t =
   | Error e -> Fmt.failwith "secmod_eddsa initialization failure: %s." e
   | Ok t -> t
 
-(*
-  - sign
-  - expose future_sk list
+let sm_key_pub = t.sm_key_pub
+let keys () = List.map (fun { priv= _; pub; t1; t2 } -> (pub, t1, t2)) t.keys
+let sign_with_sm_key s = EddsaSignature.sign ~key:t.sm_key_priv s
+
+let sign ~pub s =
+  match List.find_opt (fun k -> k.pub = pub) t.keys with
+  | None -> Error "key not found"
+  | Some k ->
+      let data = EddsaSignature.sign ~key:k.priv s in
+      Ok data
+
+(* TODO
+  - sign: check time
   - purge
   - revoke
   - schedule tasks
   - !lock
 
-  todo taler doc/config is confusing
+  taler doc/config is confusing
   how is computed stamp_expire stamp_end
   what to do of 'Exchange.signkey_legal_duration'
   => (??)