diff --git a/src/json/json_helper.c b/src/json/json_helper.c
index 7c5f7dde2..96e41b5e3 100644
--- a/src/json/json_helper.c
+++ b/src/json/json_helper.c
@@ -26,6 +26,25 @@
 #include "taler_json_lib.h"
 
 
+/**
+ * Convert string value to numeric cipher value.
+ *
+ * @param cipher_s input string
+ * @return numeric cipher value
+ */
+static enum TALER_DenominationCipher
+string_to_cipher (const char *cipher_s)
+{
+  if (0 == strcasecmp (cipher_s,
+                       "RSA"))
+    return TALER_DENOMINATION_RSA;
+  if (0 == strcasecmp (cipher_s,
+                       "CS"))
+    return TALER_DENOMINATION_CS;
+  return TALER_DENOMINATION_INVALID;
+}
+
+
 json_t *
 TALER_JSON_from_amount (const struct TALER_Amount *amount)
 {
@@ -229,9 +248,9 @@ parse_denom_pub (void *cls,
                  struct GNUNET_JSON_Specification *spec)
 {
   struct TALER_DenominationPublicKey *denom_pub = spec->ptr;
-  uint32_t cipher;
+  const char *cipher;
   struct GNUNET_JSON_Specification dspec[] = {
-    GNUNET_JSON_spec_uint32 ("cipher",
+    GNUNET_JSON_spec_string ("cipher",
                              &cipher),
     GNUNET_JSON_spec_uint32 ("age_mask",
                              &denom_pub->age_mask.mask),
@@ -250,7 +269,7 @@ parse_denom_pub (void *cls,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-  denom_pub->cipher = (enum TALER_DenominationCipher) cipher;
+  denom_pub->cipher = string_to_cipher (cipher);
   switch (denom_pub->cipher)
   {
   case TALER_DENOMINATION_RSA:
@@ -346,9 +365,9 @@ parse_denom_sig (void *cls,
                  struct GNUNET_JSON_Specification *spec)
 {
   struct TALER_DenominationSignature *denom_sig = spec->ptr;
-  uint32_t cipher;
+  const char *cipher;
   struct GNUNET_JSON_Specification dspec[] = {
-    GNUNET_JSON_spec_uint32 ("cipher",
+    GNUNET_JSON_spec_string ("cipher",
                              &cipher),
     GNUNET_JSON_spec_end ()
   };
@@ -365,7 +384,7 @@ parse_denom_sig (void *cls,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-  denom_sig->cipher = (enum TALER_DenominationCipher) cipher;
+  denom_sig->cipher = string_to_cipher (cipher);
   switch (denom_sig->cipher)
   {
   case TALER_DENOMINATION_RSA:
@@ -462,9 +481,9 @@ parse_blinded_denom_sig (void *cls,
                          struct GNUNET_JSON_Specification *spec)
 {
   struct TALER_BlindedDenominationSignature *denom_sig = spec->ptr;
-  uint32_t cipher;
+  const char *cipher;
   struct GNUNET_JSON_Specification dspec[] = {
-    GNUNET_JSON_spec_uint32 ("cipher",
+    GNUNET_JSON_spec_string ("cipher",
                              &cipher),
     GNUNET_JSON_spec_end ()
   };
@@ -481,7 +500,7 @@ parse_blinded_denom_sig (void *cls,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-  denom_sig->cipher = (enum TALER_DenominationCipher) cipher;
+  denom_sig->cipher = string_to_cipher (cipher);
   switch (denom_sig->cipher)
   {
   case TALER_DENOMINATION_RSA:
@@ -581,9 +600,9 @@ parse_blinded_planchet (void *cls,
                         struct GNUNET_JSON_Specification *spec)
 {
   struct TALER_BlindedPlanchet *blinded_planchet = spec->ptr;
-  uint32_t cipher;
+  const char *cipher;
   struct GNUNET_JSON_Specification dspec[] = {
-    GNUNET_JSON_spec_uint32 ("cipher",
+    GNUNET_JSON_spec_string ("cipher",
                              &cipher),
     GNUNET_JSON_spec_end ()
   };
@@ -600,7 +619,7 @@ parse_blinded_planchet (void *cls,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-  blinded_planchet->cipher = (enum TALER_DenominationCipher) cipher;
+  blinded_planchet->cipher = string_to_cipher (cipher);
   switch (blinded_planchet->cipher)
   {
   case TALER_DENOMINATION_RSA:
@@ -704,9 +723,9 @@ parse_exchange_withdraw_values (void *cls,
                                 struct GNUNET_JSON_Specification *spec)
 {
   struct TALER_ExchangeWithdrawValues *ewv = spec->ptr;
-  uint32_t cipher;
+  const char *cipher;
   struct GNUNET_JSON_Specification dspec[] = {
-    GNUNET_JSON_spec_uint32 ("cipher",
+    GNUNET_JSON_spec_string ("cipher",
                              &cipher),
     GNUNET_JSON_spec_end ()
   };
@@ -723,8 +742,8 @@ parse_exchange_withdraw_values (void *cls,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
-  ewv->cipher = (enum TALER_DenominationCipher) cipher;
-  switch (cipher)
+  ewv->cipher = string_to_cipher (cipher);
+  switch (ewv->cipher)
   {
   case TALER_DENOMINATION_RSA:
     return GNUNET_OK;
diff --git a/src/json/json_pack.c b/src/json/json_pack.c
index 535e8fa1c..8f888eaf0 100644
--- a/src/json/json_pack.c
+++ b/src/json/json_pack.c
@@ -61,8 +61,8 @@ TALER_JSON_pack_denom_pub (
   case TALER_DENOMINATION_RSA:
     ps.object
       = GNUNET_JSON_PACK (
-          GNUNET_JSON_pack_uint64 ("cipher",
-                                   TALER_DENOMINATION_RSA),
+          GNUNET_JSON_pack_string ("cipher",
+                                   "RSA"),
           GNUNET_JSON_pack_uint64 ("age_mask",
                                    pk->age_mask.mask),
           GNUNET_JSON_pack_rsa_public_key ("rsa_public_key",
@@ -71,8 +71,8 @@ TALER_JSON_pack_denom_pub (
   case TALER_DENOMINATION_CS:
     ps.object
       = GNUNET_JSON_PACK (
-          GNUNET_JSON_pack_uint64 ("cipher",
-                                   TALER_DENOMINATION_CS),
+          GNUNET_JSON_pack_string ("cipher",
+                                   "CS"),
           GNUNET_JSON_pack_uint64 ("age_mask",
                                    pk->age_mask.mask),
           GNUNET_JSON_pack_data_varsize ("cs_public_key",
@@ -99,15 +99,15 @@ TALER_JSON_pack_denom_sig (
   {
   case TALER_DENOMINATION_RSA:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_RSA),
+      GNUNET_JSON_pack_string ("cipher",
+                               "RSA"),
       GNUNET_JSON_pack_rsa_signature ("rsa_signature",
                                       sig->details.rsa_signature));
     break;
   case TALER_DENOMINATION_CS:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_CS),
+      GNUNET_JSON_pack_string ("cipher",
+                               "CS"),
       GNUNET_JSON_pack_data_auto ("cs_signature_r",
                                   &sig->details.cs_signature.r_point),
       GNUNET_JSON_pack_data_auto ("cs_signature_s",
@@ -133,13 +133,13 @@ TALER_JSON_pack_exchange_withdraw_values (
   {
   case TALER_DENOMINATION_RSA:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_RSA));
+      GNUNET_JSON_pack_string ("cipher",
+                               "RSA"));
     break;
   case TALER_DENOMINATION_CS:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_CS),
+      GNUNET_JSON_pack_string ("cipher",
+                               "CS"),
       GNUNET_JSON_pack_data_varsize (
         "r_pub_0",
         &ewv->details.cs_values.r_pub[0],
@@ -170,15 +170,15 @@ TALER_JSON_pack_blinded_denom_sig (
   {
   case TALER_DENOMINATION_RSA:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_RSA),
+      GNUNET_JSON_pack_string ("cipher",
+                               "RSA"),
       GNUNET_JSON_pack_rsa_signature ("blinded_rsa_signature",
                                       sig->details.blinded_rsa_signature));
     break;
   case TALER_DENOMINATION_CS:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_CS),
+      GNUNET_JSON_pack_string ("cipher",
+                               "CS"),
       GNUNET_JSON_pack_uint64 ("b",
                                sig->details.blinded_cs_answer.b),
       GNUNET_JSON_pack_data_auto ("s",
@@ -204,8 +204,8 @@ TALER_JSON_pack_blinded_planchet (
   {
   case TALER_DENOMINATION_RSA:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_RSA),
+      GNUNET_JSON_pack_string ("cipher",
+                               "RSA"),
       GNUNET_JSON_pack_data_varsize (
         "rsa_blinded_planchet",
         blinded_planchet->details.rsa_blinded_planchet.blinded_msg,
@@ -213,8 +213,8 @@ TALER_JSON_pack_blinded_planchet (
     break;
   case TALER_DENOMINATION_CS:
     ps.object = GNUNET_JSON_PACK (
-      GNUNET_JSON_pack_uint64 ("cipher",
-                               TALER_DENOMINATION_CS),
+      GNUNET_JSON_pack_string ("cipher",
+                               "CS"),
       GNUNET_JSON_pack_data_auto (
         "cs_nonce",
         &blinded_planchet->details.cs_blinded_planchet.nonce),
diff --git a/src/lib/exchange_api_link.c b/src/lib/exchange_api_link.c
index 6a904da1b..ff1efe15b 100644
--- a/src/lib/exchange_api_link.c
+++ b/src/lib/exchange_api_link.c
@@ -102,12 +102,10 @@ parse_link_coin (const struct TALER_EXCHANGE_LinkHandle *lh,
                                &rpub),
     TALER_JSON_spec_blinded_denom_sig ("ev_sig",
                                        &bsig),
-    // FIXME: add to spec!
     TALER_JSON_spec_exchange_withdraw_values ("ewv",
                                               &alg_values),
     GNUNET_JSON_spec_fixed_auto ("link_sig",
                                  &link_sig),
-    // FIXME: add to spec!
     GNUNET_JSON_spec_uint32 ("coin_idx",
                              &coin_idx),
     GNUNET_JSON_spec_end ()
diff --git a/src/lib/exchange_api_recoup.c b/src/lib/exchange_api_recoup.c
index a3ba18afd..2584ade92 100644
--- a/src/lib/exchange_api_recoup.c
+++ b/src/lib/exchange_api_recoup.c
@@ -322,7 +322,6 @@ TALER_EXCHANGE_recoup (struct TALER_EXCHANGE_Handle *exchange,
                                 &h_denom_pub),
     TALER_JSON_pack_denom_sig ("denom_sig",
                                denom_sig),
-    // FIXME: add this to the spec!
     TALER_JSON_pack_exchange_withdraw_values ("ewv",
                                               exchange_vals),
     GNUNET_JSON_pack_data_auto ("coin_sig",
diff --git a/src/lib/exchange_api_recoup_refresh.c b/src/lib/exchange_api_recoup_refresh.c
index 517497067..9133e5942 100644
--- a/src/lib/exchange_api_recoup_refresh.c
+++ b/src/lib/exchange_api_recoup_refresh.c
@@ -326,7 +326,6 @@ TALER_EXCHANGE_recoup_refresh (
                                 &h_denom_pub),
     TALER_JSON_pack_denom_sig ("denom_sig",
                                denom_sig),
-    // FIXME: add this to the spec!
     TALER_JSON_pack_exchange_withdraw_values ("ewv",
                                               exchange_vals),
     GNUNET_JSON_pack_data_auto ("coin_sig",