diff --git a/src/api.ml b/src/api.ml
index b38e9f5d..81e2ba7f 100644
--- a/src/api.ml
+++ b/src/api.ml
@@ -925,8 +925,10 @@ module RecoupDenoms = struct
     |> finish
 end
 
-module DenomCommon = struct
+module RsaDenom = struct
+  (* correspond to: ({ rsa_pub: RsaPublicKey;} & DenomCommon) *)
   type t = {
+    rsa_pub: RsaPublicKey.t;
     master_sig: DenominationKeyValidityPS.t;
     stamp_start: Timestamp.t;
     stamp_expire_withdraw: Timestamp.t;
@@ -936,9 +938,10 @@ module DenomCommon = struct
   }
 
   let jsont =
-    let make master_sig stamp_start stamp_expire_withdraw stamp_expire_deposit
-        stamp_expire_legal lost =
+    let make rsa_pub master_sig stamp_start stamp_expire_withdraw
+        stamp_expire_deposit stamp_expire_legal lost =
       {
+        rsa_pub;
         master_sig;
         stamp_start;
         stamp_expire_withdraw;
@@ -947,6 +950,7 @@ module DenomCommon = struct
         lost;
       }
     in
+    let rsa_pub v = v.rsa_pub in
     let master_sig v = v.master_sig in
     let stamp_start v = v.stamp_start in
     let stamp_expire_withdraw v = v.stamp_expire_withdraw in
@@ -954,7 +958,8 @@ module DenomCommon = struct
     let stamp_expire_legal v = v.stamp_expire_legal in
     let lost v = v.lost in
     let open Jsont.Object in
-    map ~kind:"DenomCommon" make
+    map ~kind:"RsaDenom" make
+    |> mem "rsa_pub" RsaPublicKey.jsont ~enc:rsa_pub
     |> mem "master_sig" DenominationKeyValidityPS.jsont ~enc:master_sig
     |> mem "stamp_start" Timestamp.jsont ~enc:stamp_start
     |> mem "stamp_expire_withdraw" Timestamp.jsont ~enc:stamp_expire_withdraw
@@ -964,9 +969,9 @@ module DenomCommon = struct
     |> finish
 end
 
-module DenomGroupRsa = struct
+module RsaDenomGroup = struct
   type t = {
-    rsa_pub: RsaPublicKey.t;
+    denoms: RsaDenom.t list;
     value: Amount.t;
     fee_withdraw: Amount.t;
     fee_deposit: Amount.t;
@@ -975,18 +980,18 @@ module DenomGroupRsa = struct
   }
 
   let jsont =
-    let make rsa_pub value fee_withdraw fee_deposit fee_refresh fee_refund =
-      { rsa_pub; value; fee_withdraw; fee_deposit; fee_refresh; fee_refund }
+    let make denoms value fee_withdraw fee_deposit fee_refresh fee_refund =
+      { denoms; value; fee_withdraw; fee_deposit; fee_refresh; fee_refund }
     in
-    let rsa_pub v = v.rsa_pub in
+    let denoms v = v.denoms in
     let value v = v.value in
     let fee_withdraw v = v.fee_withdraw in
     let fee_deposit v = v.fee_deposit in
     let fee_refresh v = v.fee_refresh in
     let fee_refund v = v.fee_refund in
     let open Jsont.Object in
-    map ~kind:"DenomGroupRsa" make
-    |> mem "rsa_pub" RsaPublicKey.jsont ~enc:rsa_pub
+    map ~kind:"RsaDenomGroup" make
+    |> mem "denoms" (Jsont.list RsaDenom.jsont) ~enc:denoms
     |> mem "value" Amount.jsont ~enc:value
     |> mem "fee_withdraw" Amount.jsont ~enc:fee_withdraw
     |> mem "fee_deposit" Amount.jsont ~enc:fee_deposit
@@ -995,29 +1000,21 @@ module DenomGroupRsa = struct
     |> finish
 end
 
+(* TODO better jsont cases
+   factorize common fields (DenomCommon/DenomGroupCommon)
+   "+age_restricted"/CS variants
+   raise error not implemented if not RSA *)
 module DenomGroup = struct
-  (* TODO
-type DenomGroup =
-  | DenomGroupRsa
-  | DenomGroupCs
-  | DenomGroupRsaAgeRestricted
-  | DenomGroupCsAgeRestricted;
-  *)
-  type t = Rsa of DenomGroupRsa.t
-
-  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"
+  type t = Rsa of RsaDenomGroup.t
 
   let of_rsa v = Rsa v
 
   let jsont =
     let open Jsont.Object in
-    let rsa = Case.map "RSA" DenomGroupRsa.jsont ~dec:of_rsa in
+    let rsa = Case.map "RSA" RsaDenomGroup.jsont ~dec:of_rsa in
     let enc_case = function Rsa v -> Case.value rsa v in
     let cases = Case.[ make rsa ] in
-    map ~kind:"DenomGroup" Fun.id
+    map ~kind:"DenominationKey" Fun.id
     |> case_mem "cipher" Jsont.string ~enc:Fun.id ~enc_case cases
     |> finish
 end