Merge branch 'master' of taler.net:exchange

15 files changed, 1074 insertions, 171 deletions

diff --git a/src/exchange-lib/exchange_api_common.c b/src/exchange-lib/exchange_api_common.c
index acf90fce6..e6ab2cbc2 100644
--- a/src/exchange-lib/exchange_api_common.c
+++ b/src/exchange-lib/exchange_api_common.c
@@ -38,8 +38,8 @@
  */
 int
 TALER_EXCHANGE_verify_coin_history (const char *currency,
-                                     const struct TALER_CoinSpendPublicKeyP *coin_pub,
-                                     json_t *history,
+				    const struct TALER_CoinSpendPublicKeyP *coin_pub,
+				    json_t *history,
                                     struct TALER_Amount *total)
 {
   size_t len;
diff --git a/src/exchange-lib/exchange_api_reserve.c b/src/exchange-lib/exchange_api_reserve.c
index 0bff767e6..9de2b268f 100644
--- a/src/exchange-lib/exchange_api_reserve.c
+++ b/src/exchange-lib/exchange_api_reserve.c
@@ -599,7 +599,7 @@ reserve_withdraw_ok (struct TALER_EXCHANGE_ReserveWithdrawHandle *wsh,
 
 
 /**
- * We got a 402 PAYMENT REQUIRED response for the /reserve/withdraw operation.
+ * We got a 403 FORBIDDEN response for the /reserve/withdraw operation.
  * Check the signatures on the withdraw transactions in the provided
  * history and that the balances add up.  We don't do anything directly
  * with the information, as the JSON will be returned to the application.
@@ -723,7 +723,7 @@ handle_reserve_withdraw_finished (void *cls,
     /* This should never happen, either us or the exchange is buggy
        (or API version conflict); just pass JSON reply to the application */
     break;
-  case MHD_HTTP_PAYMENT_REQUIRED:
+  case MHD_HTTP_FORBIDDEN:
     /* The exchange says that the reserve has insufficient funds;
        check the signatures in the history... */
     if (GNUNET_OK !=
diff --git a/src/exchange-lib/test_exchange_api.c b/src/exchange-lib/test_exchange_api.c
index 29095d87a..80007c66f 100644
--- a/src/exchange-lib/test_exchange_api.c
+++ b/src/exchange-lib/test_exchange_api.c
@@ -1009,7 +1009,7 @@ reserve_withdraw_cb (void *cls,
     cmd->details.reserve_withdraw.sig.rsa_signature
       = GNUNET_CRYPTO_rsa_signature_dup (sig->rsa_signature);
     break;
-  case MHD_HTTP_PAYMENT_REQUIRED:
+  case MHD_HTTP_FORBIDDEN:
     /* nothing to check */
     break;
   default:
@@ -2737,7 +2737,7 @@ run (void *cls)
     /* Try to overdraw funds ... */
     { .oc = OC_WITHDRAW_SIGN,
       .label = "withdraw-coin-2",
-      .expected_response_code = MHD_HTTP_PAYMENT_REQUIRED,
+      .expected_response_code = MHD_HTTP_FORBIDDEN,
       .details.reserve_withdraw.reserve_reference = "create-reserve-1",
       .details.reserve_withdraw.amount = "EUR:5" },
 
diff --git a/src/exchange/taler-exchange-httpd_admin.c b/src/exchange/taler-exchange-httpd_admin.c
index e99448f87..72cdcb7d6 100644
--- a/src/exchange/taler-exchange-httpd_admin.c
+++ b/src/exchange/taler-exchange-httpd_admin.c
@@ -89,6 +89,7 @@ TEH_ADMIN_handler_admin_add_incoming (struct TEH_RequestHandler *rh,
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_ADMIN_ADD_INCOMING_WIREFORMAT_UNSUPPORTED,
                                            "sender_account_details");
   }
   if (0 != strcasecmp (amount.currency,
@@ -100,6 +101,7 @@ TEH_ADMIN_handler_admin_add_incoming (struct TEH_RequestHandler *rh,
                 amount.currency);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_ADMIN_ADD_INCOMING_CURRENCY_UNSUPPORTED,
                                            "amount:currency");
   }
   res = TEH_DB_execute_admin_add_incoming (connection,
diff --git a/src/exchange/taler-exchange-httpd_db.c b/src/exchange/taler-exchange-httpd_db.c
index 6b27a22a6..870f7a251 100644
--- a/src/exchange/taler-exchange-httpd_db.c
+++ b/src/exchange/taler-exchange-httpd_db.c
@@ -53,7 +53,8 @@ transaction_start_label: /* we will use goto for retries */   \
                          session))                            \
   {                                                           \
     GNUNET_break (0);                                         \
-    return TEH_RESPONSE_reply_internal_db_error (connection); \
+    return TEH_RESPONSE_reply_internal_db_error (connection, \
+						 TALER_EC_DB_START_FAILED);	     \
   }
 
 /**
@@ -73,8 +74,9 @@ transaction_start_label: /* we will use goto for retries */   \
   if (GNUNET_SYSERR == transaction_commit_result)                          \
   {                                                                        \
     TALER_LOG_WARNING ("Transaction commit failed in %s\n", __FUNCTION__); \
-    return TEH_RESPONSE_reply_commit_error (connection);                   \
-  }                                                                        \
+    return TEH_RESPONSE_reply_commit_error (connection, \
+					    TALER_EC_DB_COMMIT_FAILED_HARD); \
+  }                                                       \
   if (GNUNET_NO == transaction_commit_result)                              \
   {                                                                        \
     TALER_LOG_WARNING ("Transaction commit failed in %s\n", __FUNCTION__); \
@@ -83,7 +85,8 @@ transaction_start_label: /* we will use goto for retries */   \
     TALER_LOG_WARNING ("Transaction commit failed %u times in %s\n",       \
                        transaction_retries,                                \
                        __FUNCTION__);                                      \
-    return TEH_RESPONSE_reply_commit_error (connection);                   \
+    return TEH_RESPONSE_reply_commit_error (connection, \
+					    TALER_EC_DB_COMMIT_FAILED_ON_RETRY);				\
   }                                                                        \
 } /* end of scope opened by BEGIN_TRANSACTION */
 
@@ -197,7 +200,8 @@ TEH_DB_execute_deposit (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   if (GNUNET_YES ==
       TEH_plugin->have_deposit (TEH_plugin->cls,
@@ -225,8 +229,8 @@ TEH_DB_execute_deposit (struct MHD_Connection *connection,
   if (NULL == dki)
   {
     TEH_KS_release (mks);
-    return TEH_RESPONSE_reply_arg_invalid (connection,
-                                           "denom_pub");
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+					   TALER_EC_DEPOSIT_DB_DENOMINATION_KEY_UNKNOWN);
   }
   TALER_amount_ntoh (&value,
                      &dki->issue.properties.value);
@@ -249,7 +253,8 @@ TEH_DB_execute_deposit (struct MHD_Connection *connection,
                           session);
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DEPOSIT_HISTORY_DB_ERROR);
   }
   /* Check that cost of all transactions is smaller than
      the value of the coin. */
@@ -274,7 +279,8 @@ TEH_DB_execute_deposit (struct MHD_Connection *connection,
     TALER_LOG_WARNING ("Failed to store /deposit information in database\n");
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DEPOSIT_STORE_DB_ERROR);
   }
 
   COMMIT_TRANSACTION(session, connection);
@@ -324,7 +330,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   dep = NULL;
   ref = NULL;
@@ -337,7 +344,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
     return TEH_RESPONSE_reply_refund_failure (connection,
-                                              MHD_HTTP_NOT_FOUND);
+					      MHD_HTTP_NOT_FOUND,
+					      TALER_EC_REFUND_COIN_NOT_FOUND);
   }
   deposit_found = GNUNET_NO;
   refund_found = GNUNET_NO;
@@ -411,7 +419,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
                           session);
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
-    return TEH_RESPONSE_reply_transaction_unknown (connection);
+    return TEH_RESPONSE_reply_transaction_unknown (connection,
+						   TALER_EC_REFUND_DEPOSIT_NOT_FOUND);
   }
   /* handle if conflicting refund found */
   if (GNUNET_SYSERR == refund_found)
@@ -449,7 +458,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
     return TEH_RESPONSE_reply_refund_failure (connection,
-                                              MHD_HTTP_PRECONDITION_FAILED);
+                                              MHD_HTTP_PRECONDITION_FAILED,
+					      TALER_EC_REFUND_CURRENCY_MISSMATCH);
   }
 
   /* check if we already send the money for the /deposit */
@@ -466,6 +476,7 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_REFUND_DB_INCONSISTENT,
                                               "database inconsistent");
   }
   if (GNUNET_YES == done)
@@ -476,7 +487,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
     return TEH_RESPONSE_reply_refund_failure (connection,
-                                              MHD_HTTP_GONE);
+                                              MHD_HTTP_GONE,
+					      TALER_EC_REFUND_MERCHANT_ALREADY_PAID);
   }
 
   /* check refund amount is sufficiently low */
@@ -487,7 +499,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
     return TEH_RESPONSE_reply_refund_failure (connection,
-                                              MHD_HTTP_PRECONDITION_FAILED);
+                                              MHD_HTTP_PRECONDITION_FAILED,
+					      TALER_EC_REFUND_INSUFFICIENT_FUNDS);
   }
 
   /* Check refund fee matches fee of denomination key! */
@@ -504,6 +517,7 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_REFUND_DENOMINATION_KEY_NOT_FOUND,
                                               "denomination key not found");
   }
   TALER_amount_ntoh (&expect_fee,
@@ -519,6 +533,7 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFUND_FEE_TOO_LOW,
                                            "refund_fee");
   }
   if (1 == fee_cmp)
@@ -538,7 +553,8 @@ TEH_DB_execute_refund (struct MHD_Connection *connection,
     TALER_LOG_WARNING ("Failed to store /refund information in database\n");
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFUND_STORE_DB_ERROR);
   }
   COMMIT_TRANSACTION(session, connection);
 
@@ -566,7 +582,8 @@ TEH_DB_execute_reserve_status (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   rh = TEH_plugin->get_reserve_history (TEH_plugin->cls,
                                         session,
@@ -637,6 +654,7 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_WITHDRAW_RESERVE_UNKNOWN,
                                            "reserve_pub");
   }
 
@@ -653,7 +671,8 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
   {
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_WITHDRAW_AMOUNT_FEE_OVERFLOW);
   }
 
   /* calculate balance of the reserve */
@@ -673,7 +692,8 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
         {
           TEH_plugin->rollback (TEH_plugin->cls,
                                 session);
-          return TEH_RESPONSE_reply_internal_db_error (connection);
+          return TEH_RESPONSE_reply_internal_db_error (connection,
+						       TALER_EC_WITHDRAW_AMOUNT_DEPOSITS_OVERFLOW);
         }
       res |= 1;
       break;
@@ -686,7 +706,8 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
         GNUNET_break (0);
         TEH_plugin->rollback (TEH_plugin->cls,
                               session);
-        return TEH_RESPONSE_reply_internal_db_error (connection);
+        return TEH_RESPONSE_reply_internal_db_error (connection,
+						     TALER_EC_WITHDRAW_HISTORIC_DENOMINATION_KEY_NOT_FOUND);
       }
       TALER_amount_ntoh (&value,
                          &tdki->issue.properties.value);
@@ -700,7 +721,8 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
         {
           TEH_plugin->rollback (TEH_plugin->cls,
                                 session);
-          return TEH_RESPONSE_reply_internal_db_error (connection);
+          return TEH_RESPONSE_reply_internal_db_error (connection,
+						       TALER_EC_WITHDRAW_AMOUNT_WITHDRAWALS_OVERFLOW);
         }
       res |= 2;
       break;
@@ -708,9 +730,10 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
   }
   if (0 == (res & 1))
   {
-    /* did not encounter any deposit operations, how can we have a reserve? */
+    /* did not encounter any wire transfer operations, how can we have a reserve? */
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_WITHDRAW_RESERVE_WITHOUT_WIRE_TRANSFER);
   }
   if (0 == (res & 2))
   {
@@ -748,6 +771,7 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_WITHDRAW_SIGNATURE_FAILED,
                                               "Internal error");
   }
   collectable.sig = *denom_sig;
@@ -765,7 +789,8 @@ execute_reserve_withdraw_transaction (struct MHD_Connection *connection,
     GNUNET_break (0);
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_WITHDRAW_DB_STORE_ERROR);
   }
   COMMIT_TRANSACTION (session, connection);
 
@@ -811,7 +836,8 @@ TEH_DB_execute_reserve_withdraw (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   res = TEH_plugin->get_withdraw_info (TEH_plugin->cls,
                                        session,
@@ -820,7 +846,8 @@ TEH_DB_execute_reserve_withdraw (struct MHD_Connection *connection,
   if (GNUNET_SYSERR == res)
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_WITHDRAW_DB_FETCH_ERROR);
   }
 
   /* Don't sign again if we have already signed the coin */
@@ -834,6 +861,7 @@ TEH_DB_execute_reserve_withdraw (struct MHD_Connection *connection,
   }
   GNUNET_assert (GNUNET_NO == res);
 
+  /* FIXME: do we have to do this a second time here? */
   key_state = TEH_KS_acquire ();
   dki = TEH_KS_denomination_key_lookup (key_state,
                                         denomination_pub,
@@ -843,9 +871,11 @@ TEH_DB_execute_reserve_withdraw (struct MHD_Connection *connection,
     TEH_KS_release (key_state);
     return TEH_RESPONSE_reply_json_pack (connection,
                                          MHD_HTTP_NOT_FOUND,
-                                         "{s:s}",
+                                         "{s:s, s:I}",
                                          "error",
-                                         "Denomination not found");
+                                         "Denomination not found",
+					 "code",
+					 (json_int_t) TALER_EC_WITHDRAW_DENOMINATION_KEY_NOT_FOUND);
   }
   denom_sig.rsa_signature = NULL;
   res = execute_reserve_withdraw_transaction (connection,
@@ -901,8 +931,9 @@ refresh_check_melt (struct MHD_Connection *connection,
                                        TEH_KS_DKU_DEPOSIT);
   if (NULL == dk)
     return (MHD_YES ==
-            TEH_RESPONSE_reply_arg_unknown (connection,
-                                            "denom_pub"))
+            TEH_RESPONSE_reply_internal_error (connection,
+					       TALER_EC_REFRESH_MELT_DB_DENOMINATION_KEY_NOT_FOUND,
+					       "denomination key no longer available while executing transaction"))
         ? GNUNET_NO : GNUNET_SYSERR;
   dki = &dk->issue;
   TALER_amount_ntoh (&coin_value,
@@ -922,7 +953,8 @@ refresh_check_melt (struct MHD_Connection *connection,
     TEH_plugin->free_coin_transaction_list (TEH_plugin->cls,
                                             tl);
     return (MHD_YES ==
-            TEH_RESPONSE_reply_internal_db_error (connection))
+            TEH_RESPONSE_reply_internal_db_error (connection,
+						  TALER_EC_REFRESH_MELT_COIN_HISTORY_COMPUTATION_FAILED))
       ? GNUNET_NO : GNUNET_SYSERR;
   }
   /* Refuse to refresh when the coin's value is insufficient
@@ -995,7 +1027,8 @@ TEH_DB_execute_refresh_melt (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   START_TRANSACTION (session, connection);
   res = TEH_plugin->get_refresh_session (TEH_plugin->cls,
@@ -1015,14 +1048,15 @@ TEH_DB_execute_refresh_melt (struct MHD_Connection *connection,
   {
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_MELT_DB_FETCH_ERROR);
   }
 
   /* store 'global' session data */
   refresh_session.num_newcoins = num_new_denoms;
   refresh_session.noreveal_index
-      = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG,
-                                  TALER_CNC_KAPPA);
+    = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG,
+				TALER_CNC_KAPPA);
   key_state = TEH_KS_acquire ();
   if (GNUNET_OK !=
       (res = refresh_check_melt (connection,
@@ -1047,7 +1081,8 @@ TEH_DB_execute_refresh_melt (struct MHD_Connection *connection,
   {
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_MELT_DB_STORE_SESSION_ERROR);
   }
 
   /* store requested new denominations */
@@ -1060,7 +1095,8 @@ TEH_DB_execute_refresh_melt (struct MHD_Connection *connection,
   {
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_MELT_DB_STORE_ORDER_ERROR);
   }
 
   if (GNUNET_OK !=
@@ -1072,7 +1108,8 @@ TEH_DB_execute_refresh_melt (struct MHD_Connection *connection,
   {
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_MELT_DB_STORE_ORDER_ERROR);
   }
   if (GNUNET_OK !=
       TEH_plugin->insert_refresh_transfer_public_key (TEH_plugin->cls,
@@ -1082,7 +1119,8 @@ TEH_DB_execute_refresh_melt (struct MHD_Connection *connection,
   {
     TEH_plugin->rollback (TEH_plugin->cls,
                           session);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_MELT_DB_STORE_TRANSFER_ERROR);
   }
 
   COMMIT_TRANSACTION (session, connection);
@@ -1126,8 +1164,6 @@ check_commitment (struct MHD_Connection *connection,
   struct TALER_TransferSecretP transfer_secret;
   unsigned int j;
 
-  /* FIXME: instead of consulting DB, reconstruct everything
-     from transfer_priv here! */
   TALER_link_reveal_transfer_secret (transfer_priv,
                                      &melt->coin.coin_pub,
                                      &transfer_secret);
@@ -1158,8 +1194,10 @@ check_commitment (struct MHD_Connection *connection,
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                   "Blind failed (bad denomination key!?)\n");
-      return (MHD_YES == TEH_RESPONSE_reply_internal_error (connection,
-                                                            "Blinding error"))
+      return (MHD_YES ==
+	      TEH_RESPONSE_reply_internal_error (connection,
+						 TALER_EC_REFRESH_REVEAL_BLINDING_ERROR,
+						 "Blinding error"))
         ? GNUNET_NO : GNUNET_SYSERR;
     }
     GNUNET_CRYPTO_hash_context_read (hash_context,
@@ -1274,7 +1312,8 @@ execute_refresh_reveal_transaction (struct MHD_Connection *connection,
                                           j);
     if (NULL == ev_sigs[j].rsa_signature)
     {
-      ret = TEH_RESPONSE_reply_internal_db_error (connection);
+      ret = TEH_RESPONSE_reply_internal_db_error (connection,
+						  TALER_EC_REFRESH_REVEAL_SIGNING_ERROR);
       goto cleanup;
     }
   }
@@ -1323,7 +1362,8 @@ TEH_DB_execute_refresh_reveal (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
 
   res = TEH_plugin->get_refresh_session (TEH_plugin->cls,
@@ -1332,10 +1372,12 @@ TEH_DB_execute_refresh_reveal (struct MHD_Connection *connection,
                                          &refresh_session);
   if (GNUNET_NO == res)
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFRESH_REVEAL_SESSION_UNKNOWN,
                                            "session_hash");
   if ( (GNUNET_SYSERR == res) ||
        (refresh_session.noreveal_index >= TALER_CNC_KAPPA) )
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_REVEAL_DB_FETCH_SESSION_ERROR);
   denom_pubs = GNUNET_new_array (refresh_session.num_newcoins,
                                  struct TALER_DenominationPublicKey);
   if (GNUNET_OK !=
@@ -1349,7 +1391,8 @@ TEH_DB_execute_refresh_reveal (struct MHD_Connection *connection,
     GNUNET_free (denom_pubs);
     GNUNET_CRYPTO_rsa_signature_free (refresh_session.melt.coin.denom_sig.rsa_signature);
     GNUNET_CRYPTO_rsa_public_key_free (refresh_session.melt.coin.denom_pub.rsa_public_key);
-    return (MHD_YES == TEH_RESPONSE_reply_internal_db_error (connection))
+    return (MHD_YES == TEH_RESPONSE_reply_internal_db_error (connection,
+							     TALER_EC_REFRESH_REVEAL_DB_FETCH_ORDER_ERROR))
         ? GNUNET_NO : GNUNET_SYSERR;
   }
 
@@ -1373,7 +1416,8 @@ TEH_DB_execute_refresh_reveal (struct MHD_Connection *connection,
         GNUNET_CRYPTO_rsa_signature_free (refresh_session.melt.coin.denom_sig.rsa_signature);
         GNUNET_CRYPTO_rsa_public_key_free (refresh_session.melt.coin.denom_pub.rsa_public_key);
         GNUNET_CRYPTO_hash_context_abort (hash_context);
-        return (MHD_YES == TEH_RESPONSE_reply_internal_db_error (connection))
+        return (MHD_YES == TEH_RESPONSE_reply_internal_db_error (connection,
+								 TALER_EC_REFRESH_REVEAL_DB_FETCH_TRANSFER_ERROR))
           ? GNUNET_NO : GNUNET_SYSERR;
       }
       GNUNET_CRYPTO_hash_context_read (hash_context,
@@ -1410,7 +1454,8 @@ TEH_DB_execute_refresh_reveal (struct MHD_Connection *connection,
       GNUNET_CRYPTO_rsa_signature_free (refresh_session.melt.coin.denom_sig.rsa_signature);
       GNUNET_CRYPTO_rsa_public_key_free (refresh_session.melt.coin.denom_pub.rsa_public_key);
       GNUNET_CRYPTO_hash_context_abort (hash_context);
-      return (MHD_YES == TEH_RESPONSE_reply_internal_db_error (connection))
+      return (MHD_YES == TEH_RESPONSE_reply_internal_db_error (connection,
+							       TALER_EC_REFRESH_REVEAL_DB_FETCH_ORDER_ERROR))
         ? GNUNET_NO : GNUNET_SYSERR;
     }
     for (i=0;i<refresh_session.num_newcoins;i++)
@@ -1463,7 +1508,8 @@ TEH_DB_execute_refresh_reveal (struct MHD_Connection *connection,
         GNUNET_CRYPTO_rsa_signature_free (refresh_session.melt.coin.denom_sig.rsa_signature);
         GNUNET_CRYPTO_rsa_public_key_free (refresh_session.melt.coin.denom_pub.rsa_public_key);
         GNUNET_CRYPTO_hash_context_abort (hash_context);
-        return TEH_RESPONSE_reply_internal_db_error (connection);
+        return TEH_RESPONSE_reply_internal_db_error (connection,
+						     TALER_EC_REFRESH_REVEAL_DB_FETCH_COMMIT_ERROR);
       }
       /* add envelopes to hash_context */
       for (j=0;j<refresh_session.num_newcoins;j++)
@@ -1656,7 +1702,8 @@ TEH_DB_execute_refresh_link (struct MHD_Connection *connection,
   if (NULL == (ctx.session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   ctx.connection = connection;
   ctx.num_sessions = 0;
@@ -1680,6 +1727,7 @@ TEH_DB_execute_refresh_link (struct MHD_Connection *connection,
   GNUNET_assert (GNUNET_OK == ctx.status);
   if (0 == ctx.num_sessions)
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_REFRESH_LINK_COIN_UNKNOWN,
                                            "coin_pub");
   res = TEH_RESPONSE_reply_refresh_link_success (connection,
                                                  ctx.num_sessions,
@@ -1720,7 +1768,8 @@ TEH_DB_execute_admin_add_incoming (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   ret = TEH_plugin->reserves_in_insert (TEH_plugin->cls,
                                         session,
@@ -1732,7 +1781,8 @@ TEH_DB_execute_admin_add_incoming (struct MHD_Connection *connection,
   if (GNUNET_SYSERR == ret)
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_ADMIN_ADD_INCOMING_DB_STORE);
   }
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_OK,
@@ -1913,7 +1963,8 @@ TEH_DB_execute_track_transfer (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   ctx.is_valid = GNUNET_NO;
   ctx.wdd_head = NULL;
@@ -1926,18 +1977,21 @@ TEH_DB_execute_track_transfer (struct MHD_Connection *connection,
   if (GNUNET_SYSERR == ret)
   {
     GNUNET_break (0);
-    ret = TEH_RESPONSE_reply_internal_db_error (connection);
+    ret = TEH_RESPONSE_reply_internal_db_error (connection,
+						TALER_EC_TRACK_TRANSFER_DB_FETCH_FAILED);
     goto cleanup;
   }
   if (GNUNET_SYSERR == ctx.is_valid)
   {
     GNUNET_break (0);
-    ret = TEH_RESPONSE_reply_internal_db_error (connection);
+    ret = TEH_RESPONSE_reply_internal_db_error (connection,
+						TALER_EC_TRACK_TRANSFER_DB_INCONSISTENT);
     goto cleanup;
   }
   if (GNUNET_NO == ctx.is_valid)
   {
     ret = TEH_RESPONSE_reply_arg_unknown (connection,
+					  TALER_EC_TRACK_TRANSFER_WTID_NOT_FOUND,
                                           "wtid");
     goto cleanup;
   }
@@ -2035,7 +2089,8 @@ handle_wtid_data (void *cls,
                                coin_fee))
     {
       GNUNET_break (0);
-      ctx->res = TEH_RESPONSE_reply_internal_db_error (ctx->connection);
+      ctx->res = TEH_RESPONSE_reply_internal_db_error (ctx->connection,
+						       TALER_EC_TRACK_TRANSACTION_DB_FEE_INCONSISTENT);
     }
     else
     {
@@ -2079,7 +2134,8 @@ TEH_DB_execute_track_transaction (struct MHD_Connection *connection,
   if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DB_SETUP_FAILED);
   }
   ctx.connection = connection;
   ctx.h_contract = *h_contract;
@@ -2100,17 +2156,20 @@ TEH_DB_execute_track_transaction (struct MHD_Connection *connection,
   {
     GNUNET_break (0);
     GNUNET_break (GNUNET_SYSERR == ctx.res);
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_TRACK_TRANSACTION_DB_FETCH_FAILED);
   }
   if (GNUNET_NO == ret)
   {
     GNUNET_break (GNUNET_SYSERR == ctx.res);
-    return TEH_RESPONSE_reply_transaction_unknown (connection);
+    return TEH_RESPONSE_reply_transaction_unknown (connection,
+						   TALER_EC_TRACK_TRANSACTION_NOT_FOUND);
   }
   if (GNUNET_SYSERR == ctx.res)
   {
     GNUNET_break (0);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TRACK_TRANSACTION_WTID_RESOLUTION_ERROR,
                                               "bug resolving deposit wtid");
   }
   return ctx.res;
diff --git a/src/exchange/taler-exchange-httpd_deposit.c b/src/exchange/taler-exchange-httpd_deposit.c
index a97dd0514..b0ab42e7f 100644
--- a/src/exchange/taler-exchange-httpd_deposit.c
+++ b/src/exchange/taler-exchange-httpd_deposit.c
@@ -48,12 +48,9 @@
  */
 static int
 verify_and_execute_deposit (struct MHD_Connection *connection,
-                            const struct TALER_EXCHANGEDB_Deposit *deposit)
+			    const struct TALER_EXCHANGEDB_Deposit *deposit)
 {
-  struct TEH_KS_StateHandle *key_state;
   struct TALER_DepositRequestPS dr;
-  struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki;
-  struct TALER_Amount fee_deposit;
 
   dr.purpose.purpose = htonl (TALER_SIGNATURE_WALLET_COIN_DEPOSIT);
   dr.purpose.size = htonl (sizeof (struct TALER_DepositRequestPS));
@@ -76,39 +73,9 @@ verify_and_execute_deposit (struct MHD_Connection *connection,
   {
     TALER_LOG_WARNING ("Invalid signature on /deposit request\n");
     return TEH_RESPONSE_reply_signature_invalid (connection,
+						 TALER_EC_DEPOSIT_COIN_SIGNATURE_INVALID,
                                                  "coin_sig");
   }
-  /* check denomination exists and is valid */
-  key_state = TEH_KS_acquire ();
-  dki = TEH_KS_denomination_key_lookup (key_state,
-                                        &deposit->coin.denom_pub,
-					TEH_KS_DKU_DEPOSIT);
-  if (NULL == dki)
-  {
-    TEH_KS_release (key_state);
-    TALER_LOG_WARNING ("Unknown denomination key in /deposit request\n");
-    return TEH_RESPONSE_reply_arg_unknown (connection,
-                                           "denom_pub");
-  }
-  /* check coin signature */
-  if (GNUNET_YES !=
-      TALER_test_coin_valid (&deposit->coin))
-  {
-    TALER_LOG_WARNING ("Invalid coin passed for /deposit\n");
-    TEH_KS_release (key_state);
-    return TEH_RESPONSE_reply_signature_invalid (connection,
-                                                 "ub_sig");
-  }
-  TALER_amount_ntoh (&fee_deposit,
-                     &dki->issue.properties.fee_deposit);
-  if (0 < TALER_amount_cmp (&fee_deposit,
-                            &deposit->amount_with_fee))
-  {
-    TEH_KS_release (key_state);
-    return TEH_RESPONSE_reply_external_error (connection,
-                                              "deposited amount smaller than depositing fee");
-  }
-  TEH_KS_release (key_state);
 
   return TEH_DB_execute_deposit (connection,
                                  deposit);
@@ -141,12 +108,11 @@ TEH_DEPOSIT_handler_deposit (struct TEH_RequestHandler *rh,
   json_t *wire;
   struct TALER_EXCHANGEDB_Deposit deposit;
   struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki;
-  struct TEH_KS_StateHandle *ks;
+  struct TEH_KS_StateHandle *key_state;
   struct GNUNET_HashCode my_h_wire;
-  struct TALER_Amount amount;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_json ("wire", &wire),
-    TALER_JSON_spec_amount ("f", &amount),
+    TALER_JSON_spec_amount ("f", &deposit.amount_with_fee),
     TALER_JSON_spec_denomination_public_key ("denom_pub", &deposit.coin.denom_pub),
     TALER_JSON_spec_denomination_signature ("ub_sig", &deposit.coin.denom_sig),
     GNUNET_JSON_spec_fixed_auto ("coin_pub", &deposit.coin.coin_pub),
@@ -180,11 +146,13 @@ TEH_DEPOSIT_handler_deposit (struct TEH_RequestHandler *rh,
   if (GNUNET_NO == res)
     return MHD_YES; /* failure */
 
+  deposit.receiver_wire_account = wire;
   if (deposit.refund_deadline.abs_value_us > deposit.wire_deadline.abs_value_us)
   {
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_DEPOSIT_REFUND_DEADLINE_AFTER_WIRE_DEADLINE,
                                            "refund_deadline");
   }
 
@@ -194,6 +162,7 @@ TEH_DEPOSIT_handler_deposit (struct TEH_RequestHandler *rh,
   {
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_DEPOSIT_INVALID_WIRE_FORMAT,
                                            "wire");
   }
   if (GNUNET_OK !=
@@ -203,6 +172,7 @@ TEH_DEPOSIT_handler_deposit (struct TEH_RequestHandler *rh,
     TALER_LOG_WARNING ("Failed to parse JSON wire format specification for /deposit request\n");
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_DEPOSIT_INVALID_WIRE_FORMAT_JSON,
                                            "wire");
   }
   if (0 != memcmp (&deposit.h_wire,
@@ -212,32 +182,48 @@ TEH_DEPOSIT_handler_deposit (struct TEH_RequestHandler *rh,
     /* Client hashed contract differently than we did, reject */
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_DEPOSIT_INVALID_WIRE_FORMAT_CONTRACT_HASH_CONFLICT,
                                            "H_wire");
   }
-  ks = TEH_KS_acquire ();
-  dki = TEH_KS_denomination_key_lookup (ks,
+
+  /* check denomination exists and is valid */
+  key_state = TEH_KS_acquire ();
+  dki = TEH_KS_denomination_key_lookup (key_state,
                                         &deposit.coin.denom_pub,
 					TEH_KS_DKU_DEPOSIT);
   if (NULL == dki)
   {
-    TEH_KS_release (ks);
-    GNUNET_JSON_parse_free (spec);
+    TEH_KS_release (key_state);
+    TALER_LOG_WARNING ("Unknown denomination key in /deposit request\n");
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_DEPOSIT_DENOMINATION_KEY_UNKNOWN,
                                            "denom_pub");
   }
   TALER_amount_ntoh (&deposit.deposit_fee,
                      &dki->issue.properties.fee_deposit);
-  TEH_KS_release (ks);
-  deposit.receiver_wire_account = wire;
-  deposit.amount_with_fee = amount;
-  if (-1 == TALER_amount_cmp (&deposit.amount_with_fee,
-                              &deposit.deposit_fee))
+  /* check coin signature */
+  if (GNUNET_YES !=
+      TALER_test_coin_valid (&deposit.coin))
   {
-    /* Total amount smaller than fee, invalid */
-    GNUNET_JSON_parse_free (spec);
-    return TEH_RESPONSE_reply_arg_invalid (connection,
-                                           "f");
+    TALER_LOG_WARNING ("Invalid coin passed for /deposit\n");
+    TEH_KS_release (key_state);
+    return TEH_RESPONSE_reply_signature_invalid (connection,
+						 TALER_EC_DEPOSIT_DENOMINATION_SIGNATURE_INVALID,
+                                                 "ub_sig");
+  }
+  TALER_amount_ntoh (&deposit.deposit_fee,
+                     &dki->issue.properties.fee_deposit);
+  TEH_KS_release (key_state);
+
+  if (0 < TALER_amount_cmp (&deposit.deposit_fee,
+                            &deposit.amount_with_fee))
+  {
+    GNUNET_break_op (0);
+    return TEH_RESPONSE_reply_external_error (connection,
+					      TALER_EC_DEPOSIT_NEGATIVE_VALUE_AFTER_FEE,
+                                              "deposited amount smaller than depositing fee");
   }
+  
   res = verify_and_execute_deposit (connection,
                                     &deposit);
   GNUNET_JSON_parse_free (spec);
diff --git a/src/exchange/taler-exchange-httpd_parsing.c b/src/exchange/taler-exchange-httpd_parsing.c
index c7118c462..e9c38eb82 100644
--- a/src/exchange/taler-exchange-httpd_parsing.c
+++ b/src/exchange/taler-exchange-httpd_parsing.c
@@ -79,6 +79,7 @@ TEH_PARSE_post_json (struct MHD_Connection *connection,
   case GNUNET_JSON_PR_OUT_OF_MEMORY:
     return (MHD_NO ==
             TEH_RESPONSE_reply_internal_error (connection,
+					       TALER_EC_PARSER_OUT_OF_MEMORY,
                                                "out of memory"))
       ? GNUNET_SYSERR : GNUNET_NO;
   case GNUNET_JSON_PR_CONTINUE:
@@ -144,7 +145,9 @@ TEH_PARSE_mhd_request_arg_data (struct MHD_Connection *connection,
   if (NULL == str)
   {
     return (MHD_NO ==
-            TEH_RESPONSE_reply_arg_missing (connection, param_name))
+            TEH_RESPONSE_reply_arg_missing (connection,
+					    TALER_EC_PARAMETER_MISSING,
+					    param_name))
       ? GNUNET_SYSERR : GNUNET_NO;
   }
   if (GNUNET_OK !=
@@ -153,7 +156,9 @@ TEH_PARSE_mhd_request_arg_data (struct MHD_Connection *connection,
                                      out_data,
                                      out_size))
     return (MHD_NO ==
-            TEH_RESPONSE_reply_arg_invalid (connection, param_name))
+            TEH_RESPONSE_reply_arg_invalid (connection,
+					    TALER_EC_PARAMETER_MALFORMED,
+					    param_name))
       ? GNUNET_SYSERR : GNUNET_NO;
   return GNUNET_OK;
 }
@@ -193,8 +198,9 @@ TEH_PARSE_json_data (struct MHD_Connection *connection,
     ret = (MHD_YES ==
            TEH_RESPONSE_reply_json_pack (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         "{s:s, s:s, s:I}",
+                                         "{s:s, s:I, s:s, s:I}",
                                          "error", "parse error",
+					 "code", (json_int_t) TALER_EC_JSON_INVALID_WITH_DETAILS,
                                          "field", error_json_name,
                                          "line", (json_int_t) error_line))
       ? GNUNET_NO : GNUNET_SYSERR;
diff --git a/src/exchange/taler-exchange-httpd_refresh.c b/src/exchange/taler-exchange-httpd_refresh.c
index 0c500920d..3a8875f44 100644
--- a/src/exchange/taler-exchange-httpd_refresh.c
+++ b/src/exchange/taler-exchange-httpd_refresh.c
@@ -69,7 +69,7 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
   struct TALER_Amount total_melt;
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "melt request for session %s\n",
+              "/refresh/melt request for session %s\n",
               GNUNET_h2s (session_hash));
 
   GNUNET_assert (GNUNET_OK ==
@@ -86,6 +86,7 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
       GNUNET_break_op (0);
       TEH_KS_release (key_state);
       return TEH_RESPONSE_reply_arg_invalid (connection,
+					     TALER_EC_REFRESH_MELT_FRESH_DENOMINATION_KEY_NOT_FOUND,
                                              "new_denoms");
     }
     dki = &dk->issue;
@@ -105,6 +106,7 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
       GNUNET_break_op (0);
       TEH_KS_release (key_state);
       return TEH_RESPONSE_reply_internal_error (connection,
+						TALER_EC_REFRESH_MELT_COST_CALCULATION_OVERFLOW,
                                                 "cost calculation failure");
     }
   }
@@ -115,8 +117,9 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
   if (NULL == dk)
   {
     GNUNET_break (0);
-    return TEH_RESPONSE_reply_arg_invalid (connection,
-                                           "denom_pub");
+    return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_REFRESH_MELT_DENOMINATION_KEY_NOT_FOUND,
+					   "denom_pub");
   }
   dki = &dk->issue;
   TALER_amount_ntoh (&fee_melt,
@@ -129,6 +132,7 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
     GNUNET_break_op (0);
     TEH_KS_release (key_state);
     return TEH_RESPONSE_reply_external_error (connection,
+					      TALER_EC_REFRESH_MELT_FEES_EXCEED_CONTRIBUTION,
                                               "Melt contribution below melting fee");
   }
   TEH_KS_release (key_state);
@@ -141,8 +145,9 @@ handle_refresh_melt_binary (struct MHD_Connection *connection,
        total value of coins being generated to match! */
     return TEH_RESPONSE_reply_json_pack (connection,
                                          MHD_HTTP_BAD_REQUEST,
-                                         "{s:s}",
-                                         "error", "value mismatch");
+                                         "{s:s, s:I}",
+                                         "error", "value mismatch",
+					 "code", (json_int_t) TALER_EC_REFRESH_MELT_FEES_MISSMATCH);
   }
   return TEH_DB_execute_refresh_melt (connection,
                                       session_hash,
@@ -203,6 +208,7 @@ get_coin_public_info (struct MHD_Connection *connection,
     r_melt_detail->coin_info.denom_pub.rsa_public_key = NULL;
     return (MHD_YES ==
             TEH_RESPONSE_reply_signature_invalid (connection,
+						  TALER_EC_REFRESH_MELT_DENOMINATION_SIGNATURE_INVALID,
                                                   "denom_sig"))
       ? GNUNET_NO : GNUNET_SYSERR;
   }
@@ -237,6 +243,8 @@ verify_coin_public_info (struct MHD_Connection *connection,
   struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki;
   struct TALER_Amount fee_refresh;
 
+  /* FIXME: we lookup the dki twice during /refresh/melt.
+     This should be avoided. */
   key_state = TEH_KS_acquire ();
   dki = TEH_KS_denomination_key_lookup (key_state,
                                         &melt_detail->coin_info.denom_pub,
@@ -246,6 +254,7 @@ verify_coin_public_info (struct MHD_Connection *connection,
     TEH_KS_release (key_state);
     TALER_LOG_WARNING ("Unknown denomination key in /refresh/melt request\n");
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_REFRESH_MELT_DENOMINATION_KEY_NOT_FOUND,
                                            "denom_pub");
   }
   TALER_amount_ntoh (&fee_refresh,
@@ -266,6 +275,7 @@ verify_coin_public_info (struct MHD_Connection *connection,
     TEH_KS_release (key_state);
     return (MHD_YES ==
             TEH_RESPONSE_reply_external_error (connection,
+					       TALER_EC_REFRESH_MELT_AMOUNT_INSUFFICIENT,
                                                "melt amount smaller than melting fee"))
       ? GNUNET_NO : GNUNET_SYSERR;
   }
@@ -280,6 +290,7 @@ verify_coin_public_info (struct MHD_Connection *connection,
     GNUNET_break_op (0);
     if (MHD_YES !=
         TEH_RESPONSE_reply_signature_invalid (connection,
+					      TALER_EC_REFRESH_MELT_COIN_SIGNATURE_INVALID,
                                               "confirm_sig"))
       return GNUNET_SYSERR;
     return GNUNET_NO;
@@ -565,6 +576,7 @@ TEH_REFRESH_handler_refresh_melt (struct TEH_RequestHandler *rh,
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFRESH_MELT_CNC_COIN_ARRAY_SIZE_INVALID,
                                            "coin_evs");
   }
   if (TALER_CNC_KAPPA != json_array_size (transfer_pubs))
@@ -572,6 +584,7 @@ TEH_REFRESH_handler_refresh_melt (struct TEH_RequestHandler *rh,
     GNUNET_break_op (0);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFRESH_MELT_CNC_TRANSFER_ARRAY_SIZE_INVALID,
                                            "transfer_pubs");
   }
   res = handle_refresh_melt_json (connection,
@@ -694,6 +707,7 @@ TEH_REFRESH_handler_refresh_reveal (struct TEH_RequestHandler *rh,
     GNUNET_JSON_parse_free (spec);
     GNUNET_break_op (0);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFRESH_REVEAL_CNC_TRANSFER_ARRAY_SIZE_INVALID,
                                            "transfer_privs");
   }
   res = handle_refresh_reveal_json (connection,
diff --git a/src/exchange/taler-exchange-httpd_refund.c b/src/exchange/taler-exchange-httpd_refund.c
index fdb6f8b76..591bb188d 100644
--- a/src/exchange/taler-exchange-httpd_refund.c
+++ b/src/exchange/taler-exchange-httpd_refund.c
@@ -69,14 +69,16 @@ verify_and_execute_refund (struct MHD_Connection *connection,
   {
     GNUNET_break_op (0);
     return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFUND_FEE_CURRENCY_MISSMATCH,
                                            "refund_fee");
   }
   if (-1 == TALER_amount_cmp (&refund->refund_amount,
                               &refund->refund_fee) )
   {
     GNUNET_break_op (0);
-    return TEH_RESPONSE_reply_signature_invalid (connection,
-                                                 "refund_amount");
+    return TEH_RESPONSE_reply_arg_invalid (connection,
+					   TALER_EC_REFUND_FEE_ABOVE_AMOUNT,
+					   "refund_amount");
   }
   if (GNUNET_OK !=
       GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MERCHANT_REFUND,
@@ -86,6 +88,7 @@ verify_and_execute_refund (struct MHD_Connection *connection,
   {
     TALER_LOG_WARNING ("Invalid signature on /refund request\n");
     return TEH_RESPONSE_reply_signature_invalid (connection,
+						 TALER_EC_REFUND_MERCHANT_SIGNATURE_INVALID,
                                                  "merchant_sig");
   }
   return TEH_DB_execute_refund (connection,
diff --git a/src/exchange/taler-exchange-httpd_reserve.c b/src/exchange/taler-exchange-httpd_reserve.c
index 7098e99a2..0abe37c5a 100644
--- a/src/exchange/taler-exchange-httpd_reserve.c
+++ b/src/exchange/taler-exchange-httpd_reserve.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014,2015 GNUnet e.V.
+  Copyright (C) 2014, 2015, 2016 GNUnet e.V.
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Affero General Public License as published by the Free Software
@@ -138,6 +138,7 @@ TEH_RESERVE_handler_reserve_withdraw (struct TEH_RequestHandler *rh,
     GNUNET_JSON_parse_free (spec);
     TEH_KS_release (ks);
     return TEH_RESPONSE_reply_arg_unknown (connection,
+					   TALER_EC_WITHDRAW_DENOMINATION_KEY_NOT_FOUND,
                                            "denom_pub");
   }
   TALER_amount_ntoh (&amount,
@@ -171,6 +172,7 @@ TEH_RESERVE_handler_reserve_withdraw (struct TEH_RequestHandler *rh,
     TALER_LOG_WARNING ("Client supplied invalid signature for /reserve/withdraw request\n");
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_signature_invalid (connection,
+						 TALER_EC_WITHDRAW_RESERVE_SIGNATURE_INVALID,
                                                  "reserve_sig");
   }
   res = TEH_DB_execute_reserve_withdraw (connection,
diff --git a/src/exchange/taler-exchange-httpd_responses.c b/src/exchange/taler-exchange-httpd_responses.c
index cacd933f1..b31f22e10 100644
--- a/src/exchange/taler-exchange-httpd_responses.c
+++ b/src/exchange/taler-exchange-httpd_responses.c
@@ -132,17 +132,20 @@ TEH_RESPONSE_reply_json_pack (struct MHD_Connection *connection,
  * Send a response indicating an invalid argument.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is invalid
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_arg_invalid (struct MHD_Connection *connection,
+				enum TALER_ErrorCode ec,
                                 const char *param_name)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       "{s:s, s:s}",
+                                       "{s:s, s:I, s:s}",
                                        "error", "invalid parameter",
+				       "code", (json_int_t) ec,
                                        "parameter", param_name);
 }
 
@@ -153,17 +156,20 @@ TEH_RESPONSE_reply_arg_invalid (struct MHD_Connection *connection,
  * denomination key).
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is invalid
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_arg_unknown (struct MHD_Connection *connection,
+				enum TALER_ErrorCode ec,
                                 const char *param_name)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       "{s:s, s:s}",
+                                       "{s:s, s:I, s:s}",
                                        "error", "unknown entity referenced",
+				       "code", (json_int_t) ec,
                                        "parameter", param_name);
 }
 
@@ -172,17 +178,20 @@ TEH_RESPONSE_reply_arg_unknown (struct MHD_Connection *connection,
  * Send a response indicating an invalid signature.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is invalid
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_signature_invalid (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec,
                                       const char *param_name)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_UNAUTHORIZED,
-                                       "{s:s, s:s}",
+                                       "{s:s, s:I, s:s}",
                                        "error", "invalid signature",
+				       "code", (json_int_t) ec,
                                        "parameter", param_name);
 }
 
@@ -191,17 +200,20 @@ TEH_RESPONSE_reply_signature_invalid (struct MHD_Connection *connection,
  * Send a response indicating a missing argument.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is missing
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_arg_missing (struct MHD_Connection *connection,
+				enum TALER_ErrorCode ec,
                                 const char *param_name)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       "{ s:s, s:s}",
+                                       "{ s:s, s:I, s:s}",
                                        "error", "missing parameter",
+				       "code", (json_int_t) ec,
                                        "parameter", param_name);
 }
 
@@ -210,17 +222,20 @@ TEH_RESPONSE_reply_arg_missing (struct MHD_Connection *connection,
  * Send a response indicating permission denied.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param hint hint about why access was denied
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_permission_denied (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec,
                                       const char *hint)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_FORBIDDEN,
-                                       "{s:s, s:s}",
+                                       "{s:s, s:I, s:s}",
                                        "error", "permission denied",
+				       "code", (json_int_t) ec,
                                        "hint", hint);
 }
 
@@ -229,17 +244,20 @@ TEH_RESPONSE_reply_permission_denied (struct MHD_Connection *connection,
  * Send a response indicating an internal error.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param hint hint about the internal error's nature
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_internal_error (struct MHD_Connection *connection,
+				   enum TALER_ErrorCode ec,
                                    const char *hint)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
-                                       "{s:s, s:s}",
+                                       "{s:s, s:I, s:s}",
                                        "error", "internal error",
+				       "code", (json_int_t) ec,
                                        "hint", hint);
 }
 
@@ -248,17 +266,20 @@ TEH_RESPONSE_reply_internal_error (struct MHD_Connection *connection,
  * Send a response indicating an external error.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param hint hint about the error's nature
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_external_error (struct MHD_Connection *connection,
+				   enum TALER_ErrorCode ec,
                                    const char *hint)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       "{s:s, s:s}",
+                                       "{s:s, s:I, s:s}",
                                        "error", "client error",
+				       "code", (json_int_t) ec,
                                        "hint", hint);
 }
 
@@ -268,15 +289,18 @@ TEH_RESPONSE_reply_external_error (struct MHD_Connection *connection,
  * transaction (concurrent interference).
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @return a MHD result code
  */
 int
-TEH_RESPONSE_reply_commit_error (struct MHD_Connection *connection)
+TEH_RESPONSE_reply_commit_error (struct MHD_Connection *connection,
+				 enum TALER_ErrorCode ec)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       "{s:s}",
-                                       "error", "commit failure");
+                                       "{s:s, s:I}",
+                                       "error", "commit failure",
+				       "code", (json_int_t) ec);
 }
 
 
@@ -285,12 +309,15 @@ TEH_RESPONSE_reply_commit_error (struct MHD_Connection *connection)
  * database.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @return a MHD result code
  */
 int
-TEH_RESPONSE_reply_internal_db_error (struct MHD_Connection *connection)
+TEH_RESPONSE_reply_internal_db_error (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec)
 {
   return TEH_RESPONSE_reply_internal_error (connection,
+					    ec,
                                             "Failed to connect to database");
 }
 
@@ -332,9 +359,9 @@ TEH_RESPONSE_reply_invalid_json (struct MHD_Connection *connection)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_BAD_REQUEST,
-                                       "{s:s}",
-                                       "error",
-                                       "invalid json");
+                                       "{s:s, s:I}",
+                                       "error", "invalid json",
+				       "code", (json_int_t) TALER_EC_JSON_INVALID);
 }
 
 
@@ -556,11 +583,13 @@ TEH_RESPONSE_reply_deposit_insufficient_funds (struct MHD_Connection *connection
 
   history = compile_transaction_history (tl);
   if (NULL == history)
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_DEPOSIT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS);
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_FORBIDDEN,
-                                       "{s:s, s:o}",
+                                       "{s:s, s:I, s:o}",
                                        "error", "insufficient funds",
+				       "code", (json_int_t) TALER_EC_DEPOSIT_INSUFFICIENT_FUNDS,
                                        "history", history);
 }
 
@@ -696,8 +725,9 @@ TEH_RESPONSE_reply_refund_conflict (struct MHD_Connection *connection,
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_CONFLICT,
-                                       "{s:s, s:o}",
+                                       "{s:s, s:I, s:o}",
                                        "status", "conflicting refund",
+				       "code", (json_int_t) TALER_EC_REFUND_CONFLICT,
                                        "history", compile_transaction_history (tl));
 }
 
@@ -708,17 +738,19 @@ TEH_RESPONSE_reply_refund_conflict (struct MHD_Connection *connection,
  *
  * @param connection connection to the client
  * @param response_code response code to generate
+ * @param ec taler error code to include
  * @return MHD result code
  */
 int
 TEH_RESPONSE_reply_refund_failure (struct MHD_Connection *connection,
-                                   unsigned int response_code)
+                                   unsigned int response_code,
+				   enum TALER_ErrorCode ec)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        response_code,
-                                       "{s:s}",
-                                       "error",
-                                       "no details");
+                                       "{s:s, s:I}",
+                                       "status", "refund failure",
+				       "code", (json_int_t) ec);
 }
 
 
@@ -779,6 +811,7 @@ TEH_RESPONSE_reply_reserve_status_success (struct MHD_Connection *connection,
                                           &balance);
   if (NULL == json_history)
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_RESERVE_STATUS_DB_ERROR,
                                               "balance calculation failure");
   json_balance = TALER_JSON_from_amount (&balance);
   return TEH_RESPONSE_reply_json_pack (connection,
@@ -810,12 +843,14 @@ TEH_RESPONSE_reply_reserve_withdraw_insufficient_funds (struct MHD_Connection *c
                                           &balance);
   if (NULL == json_history)
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_WITHDRAW_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS,
                                               "balance calculation failure");
   json_balance = TALER_JSON_from_amount (&balance);
   return TEH_RESPONSE_reply_json_pack (connection,
-                                       MHD_HTTP_PAYMENT_REQUIRED,
-                                       "{s:s, s:o, s:o}",
+                                       MHD_HTTP_FORBIDDEN,
+                                       "{s:s, s:I, s:o, s:o}",
                                        "error", "Insufficient funds",
+				       "code", (json_int_t) TALER_EC_WITHDRAW_INSUFFICIENT_FUNDS,
                                        "balance", json_balance,
                                        "history", json_history);
 }
@@ -830,7 +865,7 @@ TEH_RESPONSE_reply_reserve_withdraw_insufficient_funds (struct MHD_Connection *c
  */
 int
 TEH_RESPONSE_reply_reserve_withdraw_success (struct MHD_Connection *connection,
-                                          const struct TALER_EXCHANGEDB_CollectableBlindcoin *collectable)
+					     const struct TALER_EXCHANGEDB_CollectableBlindcoin *collectable)
 {
   json_t *sig_json;
 
@@ -869,12 +904,15 @@ TEH_RESPONSE_reply_refresh_melt_insufficient_funds (struct MHD_Connection *conne
 
   history = compile_transaction_history (tl);
   if (NULL == history)
-    return TEH_RESPONSE_reply_internal_db_error (connection);
+    return TEH_RESPONSE_reply_internal_db_error (connection,
+						 TALER_EC_REFRESH_MELT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS);
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_FORBIDDEN,
-                                       "{s:s, s:o, s:o, s:o, s:o, s:o}",
+                                       "{s:s, s:I, s:o, s:o, s:o, s:o, s:o}",
                                        "error",
-                                       "insufficient funds",
+				       "insufficient funds",
+				       "code",
+				       (json_int_t) TALER_EC_REFRESH_MELT_INSUFFICIENT_FUNDS,
                                        "coin_pub",
                                        GNUNET_JSON_from_data_auto (coin_pub),
                                        "original_value",
@@ -1011,8 +1049,9 @@ TEH_RESPONSE_reply_refresh_reveal_missmatch (struct MHD_Connection *connection,
   }
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_CONFLICT,
-                                       "{s:s, s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:i}",
+                                       "{s:s, s:I, s:o, s:o, s:o, s:o, s:o, s:o, s:o, s:i}",
                                        "error", "commitment violation",
+				       "code", (json_int_t) TALER_EC_REFRESH_REVEAL_COMMITMENT_VIOLATION,
                                        "coin_sig", GNUNET_JSON_from_data_auto (&session->melt.coin_sig),
                                        "coin_pub", GNUNET_JSON_from_data_auto (&session->melt.coin.coin_pub),
                                        "melt_amount_with_fee", TALER_JSON_from_amount (&session->melt.amount_with_fee),
@@ -1089,15 +1128,18 @@ TEH_RESPONSE_reply_refresh_link_success (struct MHD_Connection *connection,
  * 404 reply.
  *
  * @param connection connection to the client
+ * @param ec Taler error code
  * @return MHD result code
  */
 int
-TEH_RESPONSE_reply_transaction_unknown (struct MHD_Connection *connection)
+TEH_RESPONSE_reply_transaction_unknown (struct MHD_Connection *connection,
+					enum TALER_ErrorCode ec)
 {
   return TEH_RESPONSE_reply_json_pack (connection,
                                        MHD_HTTP_NOT_FOUND,
-                                       "{s:s}",
-                                       "error", "Deposit unknown");
+                                       "{s:s, s:I}",
+                                       "error", "Deposit unknown",
+				       "code", (json_int_t) ec);
 }
 
 
diff --git a/src/exchange/taler-exchange-httpd_responses.h b/src/exchange/taler-exchange-httpd_responses.h
index 742a95b91..23cae16d7 100644
--- a/src/exchange/taler-exchange-httpd_responses.h
+++ b/src/exchange/taler-exchange-httpd_responses.h
@@ -29,6 +29,7 @@
 #include <jansson.h>
 #include <microhttpd.h>
 #include <pthread.h>
+#include "taler_error_codes.h"
 #include "taler-exchange-httpd.h"
 #include "taler-exchange-httpd_db.h"
 
@@ -78,11 +79,13 @@ TEH_RESPONSE_reply_json_pack (struct MHD_Connection *connection,
  * Send a response indicating an invalid signature.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is invalid
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_signature_invalid (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec,
                                       const char *param_name);
 
 
@@ -90,11 +93,13 @@ TEH_RESPONSE_reply_signature_invalid (struct MHD_Connection *connection,
  * Send a response indicating an invalid argument.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is invalid
  * @return MHD result code
  */
 int
 TEH_RESPONSE_reply_arg_invalid (struct MHD_Connection *connection,
+				enum TALER_ErrorCode ec,
                                 const char *param_name);
 
 
@@ -104,11 +109,13 @@ TEH_RESPONSE_reply_arg_invalid (struct MHD_Connection *connection,
  * denomination key).
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is invalid
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_arg_unknown (struct MHD_Connection *connection,
+				enum TALER_ErrorCode ec,
                                 const char *param_name);
 
 
@@ -116,11 +123,13 @@ TEH_RESPONSE_reply_arg_unknown (struct MHD_Connection *connection,
  * Send a response indicating a missing argument.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param param_name the parameter that is missing
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_arg_missing (struct MHD_Connection *connection,
+				enum TALER_ErrorCode ec,
                                 const char *param_name);
 
 
@@ -128,11 +137,13 @@ TEH_RESPONSE_reply_arg_missing (struct MHD_Connection *connection,
  * Send a response indicating permission denied.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param hint hint about why access was denied
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_permission_denied (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec,
                                       const char *hint);
 
 
@@ -140,11 +151,13 @@ TEH_RESPONSE_reply_permission_denied (struct MHD_Connection *connection,
  * Send a response indicating an internal error.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param hint hint about the internal error's nature
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_internal_error (struct MHD_Connection *connection,
+				   enum TALER_ErrorCode ec,
                                    const char *hint);
 
 
@@ -152,11 +165,13 @@ TEH_RESPONSE_reply_internal_error (struct MHD_Connection *connection,
  * Send a response indicating an external error.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @param hint hint about the error's nature
  * @return a MHD result code
  */
 int
 TEH_RESPONSE_reply_external_error (struct MHD_Connection *connection,
+				   enum TALER_ErrorCode ec,
                                    const char *hint);
 
 
@@ -165,21 +180,24 @@ TEH_RESPONSE_reply_external_error (struct MHD_Connection *connection,
  * transaction (concurrent interference).
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @return a MHD result code
  */
 int
-TEH_RESPONSE_reply_commit_error (struct MHD_Connection *connection);
-
+TEH_RESPONSE_reply_commit_error (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec);
 
 /**
  * Send a response indicating a failure to talk to the Exchange's
  * database.
  *
  * @param connection the MHD connection to use
+ * @param ec error code uniquely identifying the error
  * @return a MHD result code
  */
 int
-TEH_RESPONSE_reply_internal_db_error (struct MHD_Connection *connection);
+TEH_RESPONSE_reply_internal_db_error (struct MHD_Connection *connection,
+				      enum TALER_ErrorCode ec);
 
 
 /**
@@ -266,11 +284,13 @@ TEH_RESPONSE_reply_refund_conflict (struct MHD_Connection *connection,
  *
  * @param connection connection to the client
  * @param response_code response code to generate
+ * @param ec error code uniquely identifying the error
  * @return MHD result code
  */
 int
 TEH_RESPONSE_reply_refund_failure (struct MHD_Connection *connection,
-                                   unsigned int response_code);
+				   unsigned int response_code,
+				   enum TALER_ErrorCode ec);
 
 
 /**
@@ -291,10 +311,12 @@ TEH_RESPONSE_reply_refund_success (struct MHD_Connection *connection,
  * 404 reply.
  *
  * @param connection connection to the client
+ * @param ec Taler error code
  * @return MHD result code
  */
 int
-TEH_RESPONSE_reply_transaction_unknown (struct MHD_Connection *connection);
+TEH_RESPONSE_reply_transaction_unknown (struct MHD_Connection *connection,
+					enum TALER_ErrorCode ec);
 
 
 /**
@@ -307,7 +329,7 @@ TEH_RESPONSE_reply_transaction_unknown (struct MHD_Connection *connection);
  */
 int
 TEH_RESPONSE_reply_transfer_pending (struct MHD_Connection *connection,
-				    struct GNUNET_TIME_Absolute planned_exec_time);
+				     struct GNUNET_TIME_Absolute planned_exec_time);
 
 
 /**
diff --git a/src/exchange/taler-exchange-httpd_test.c b/src/exchange/taler-exchange-httpd_test.c
index 7c3252b10..731da36ce 100644
--- a/src/exchange/taler-exchange-httpd_test.c
+++ b/src/exchange/taler-exchange-httpd_test.c
@@ -295,6 +295,7 @@ TEH_TEST_handler_test_ecdhe (struct TEH_RequestHandler *rh,
   {
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TEST_ECDH_ERROR,
 					      "Failed to perform ECDH");
   }
   GNUNET_JSON_parse_free (spec);
@@ -365,6 +366,7 @@ TEH_TEST_handler_test_eddsa (struct TEH_RequestHandler *rh,
   {
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_signature_invalid (connection,
+						 TALER_EC_TEST_EDDSA_INVALID,
 						 "eddsa_sig");
   }
   GNUNET_JSON_parse_free (spec);
@@ -377,6 +379,7 @@ TEH_TEST_handler_test_eddsa (struct TEH_RequestHandler *rh,
   {
     GNUNET_free (pk);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TEST_EDDSA_ERROR,
 					      "Failed to EdDSA-sign");
   }
   GNUNET_CRYPTO_eddsa_key_get_public (pk,
@@ -419,6 +422,7 @@ TEH_TEST_handler_test_rsa_get (struct TEH_RequestHandler *rh,
   {
     GNUNET_break (0);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TEST_RSA_GEN_ERROR,
 					      "Failed to create RSA key");
   }
   pub = GNUNET_CRYPTO_rsa_private_key_get_public (rsa_pk);
@@ -426,6 +430,7 @@ TEH_TEST_handler_test_rsa_get (struct TEH_RequestHandler *rh,
   {
     GNUNET_break (0);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TEST_RSA_PUB_ERROR,
 					      "Failed to get public RSA key");
   }
   res = TEH_RESPONSE_reply_json_pack (connection,
@@ -489,6 +494,7 @@ TEH_TEST_handler_test_rsa_sign (struct TEH_RequestHandler *rh,
     GNUNET_break (0);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TEST_RSA_GEN_ERROR,
 					      "Failed to create RSA key");
   }
   sig = GNUNET_CRYPTO_rsa_sign_blinded (rsa_pk,
@@ -499,6 +505,7 @@ TEH_TEST_handler_test_rsa_sign (struct TEH_RequestHandler *rh,
     GNUNET_break (0);
     GNUNET_JSON_parse_free (spec);
     return TEH_RESPONSE_reply_internal_error (connection,
+					      TALER_EC_TEST_RSA_SIGN_ERROR,
 					      "Failed to RSA-sign");
   }
   GNUNET_JSON_parse_free (spec);
diff --git a/src/exchange/taler-exchange-httpd_tracking.c b/src/exchange/taler-exchange-httpd_tracking.c
index f4d106628..e5d1139f1 100644
--- a/src/exchange/taler-exchange-httpd_tracking.c
+++ b/src/exchange/taler-exchange-httpd_tracking.c
@@ -88,14 +88,15 @@ check_and_handle_track_transaction_request (struct MHD_Connection *connection,
   {
     GNUNET_break_op (0);
     return TEH_RESPONSE_reply_signature_invalid (connection,
+						 TALER_EC_TRACK_TRANSACTION_MERCHANT_SIGNATURE_INVALID,
 						 "merchant_sig");
   }
   return TEH_DB_execute_track_transaction (connection,
-				      &tps->h_contract,
-				      &tps->h_wire,
-				      &tps->coin_pub,
-				      merchant_pub,
-				      transaction_id);
+					   &tps->h_contract,
+					   &tps->h_wire,
+					   &tps->coin_pub,
+					   merchant_pub,
+					   transaction_id);
 }
 
 
diff --git a/src/include/taler_error_codes.h b/src/include/taler_error_codes.h
index bbb300440..3c3ddcfd4 100644
--- a/src/include/taler_error_codes.h
+++ b/src/include/taler_error_codes.h
@@ -35,10 +35,769 @@ enum TALER_ErrorCode
   /**
    * Special code to indicate no error.
    */
-  TALER_EC_NONE = 0
+  TALER_EC_NONE = 0,
 
+  /* ********** generic error codes ************* */
+  
+  /**
+   * The exchange failed to even just initialize its connection to the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DB_SETUP_FAILED = 1001,
+
+  /**
+   * The exchange encountered an error event to just start 
+   * the database transaction.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DB_START_FAILED = 1002,
+
+  /**
+   * The exchange encountered an error event to commit 
+   * the database transaction (hard, unrecoverable error).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DB_COMMIT_FAILED_HARD = 1003,
+  
+  /**
+   * The exchange encountered an error event to commit 
+   * the database transaction, even after repeatedly
+   * retrying it there was always a conflicting transaction.
+   * (This indicates a repeated serialization error; should
+   * only happen if some client maliciously tries to create
+   * conflicting concurrent transactions.)
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DB_COMMIT_FAILED_ON_RETRY = 1004,
+
+    /**
+   * The exchange had insufficient memory to parse the request. This
+   * response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_PARSER_OUT_OF_MEMORY = 1005,
+
+  /**
+   * The JSON in the client's request to the exchange was malformed.
+   * (Generic parse error).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_JSON_INVALID = 1006,
+
+  /**
+   * The JSON in the client's request to the exchange was malformed.
+   * Details about the location of the parse error are provided.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_JSON_INVALID_WITH_DETAILS = 1007,
+
+  /**
+   * A required parameter in the request to the exchange was missing.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_PARAMETER_MISSING = 1008,
+
+  /**
+   * A parameter in the request to the exchange was malformed.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_PARAMETER_MALFORMED = 1009,
+
+  /* ********** request-specific error codes ************* */  
+  
+  /**
+   * The given reserve does not have sufficient funds to admit the
+   * requested withdraw operation at this time.  The response includes
+   * the current "balance" of the reserve as well as the transaction
+   * "history" that lead to this balance.  This response is provided
+   * with HTTP status code MHD_HTTP_FORBIDDEN.
+   */
+  TALER_EC_WITHDRAW_INSUFFICIENT_FUNDS = 1100, 
+
+  /**
+   * The exchange has no information about the "reserve_pub" that
+   * was given.
+   * This response is provided with HTTP status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_WITHDRAW_RESERVE_UNKNOWN = 1101,
+
+  /**
+   * The amount to withdraw together with the fee exceeds the
+   * numeric range for Taler amounts.  This is not a client 
+   * failure, as the coin value and fees come from the exchange's
+   * configuration.
+   * This response is provided with HTTP status code MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_AMOUNT_FEE_OVERFLOW = 1102,
+  
+  /**
+   * All of the deposited amounts into this reserve total up to a
+   * value that is too big for the numeric range for Taler amounts.
+   * This is not a client failure, as the transaction history comes
+   * from the exchange's configuration.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_AMOUNT_DEPOSITS_OVERFLOW = 1103,
+
+  /**
+   * For one of the historic withdrawals from this reserve, the
+   * exchange could not find the denomination key.
+   * This is not a client failure, as the transaction history comes
+   * from the exchange's configuration.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_HISTORIC_DENOMINATION_KEY_NOT_FOUND = 1104,
+
+  /**
+   * All of the withdrawals from reserve total up to a
+   * value that is too big for the numeric range for Taler amounts.
+   * This is not a client failure, as the transaction history comes
+   * from the exchange's configuration.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_AMOUNT_WITHDRAWALS_OVERFLOW = 1105,
+
+  /**
+   * The exchange somehow knows about this reserve, but there seem to
+   * have been no wire transfers made.  This is not a client failure,
+   * as this is a database consistency issue of the exchange.  This
+   * response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_RESERVE_WITHOUT_WIRE_TRANSFER = 1106,
+
+  /**
+   * The exchange failed to create the signature using the
+   * denomination key.  This response is provided with HTTP status
+   * code MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_SIGNATURE_FAILED = 1107,
+
+  /**
+   * The exchange failed to store the withdraw operation in its
+   * database.  This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_DB_STORE_ERROR = 1108,
+
+  /**
+   * The exchange failed to check against historic withdraw data from
+   * database (as part of ensuring the idempotency of the operation).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_WITHDRAW_DB_FETCH_ERROR = 1109,
+
+  /**
+   * The exchange is not aware of the denomination key
+   * the wallet requested for the withdrawal.
+   * This response is provided
+   * with HTTP status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_WITHDRAW_DENOMINATION_KEY_NOT_FOUND = 1110,
+
+  /**
+   * The signature of the reserve is not valid.  This response is
+   * provided with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_WITHDRAW_RESERVE_SIGNATURE_INVALID = 1111,
+
+  /**
+   * The exchange failed to obtain the transaction history of the
+   * given reserve from the database while generating an insufficient
+   * funds errors.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_WITHDRAW_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS = 1112,
+  
+  /**
+   * The exchange failed to obtain the transaction history of the
+   * given reserve from the database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_RESERVE_STATUS_DB_ERROR = 1150,
+
+
+  /**
+   * The respective coin did not have sufficient residual value
+   * for the /deposit operation (i.e. due to double spending).
+   * The "history" in the respose provides the transaction history
+   * of the coin proving this fact.  This response is provided
+   * with HTTP status code MHD_HTTP_FORBIDDEN.
+   */
+  TALER_EC_DEPOSIT_INSUFFICIENT_FUNDS = 1200,
+
+  /**
+   * The exchange failed to obtain the transaction history of the
+   * given coin from the database (this does not happen merely because
+   * the coin is seen by the exchange for the first time).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DEPOSIT_HISTORY_DB_ERROR = 1201,
+
+  /**
+   * The exchange failed to store the /depost information in the
+   * database.  This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DEPOSIT_STORE_DB_ERROR = 1202,
+
+  /**
+   * The exchange database is unaware of the denomination key that
+   * signed the coin (however, the exchange process is; this is not
+   * supposed to happen; it can happen if someone decides to purge the
+   * DB behind the back of the exchange process).  Hence the deposit
+   * is being refused.  This response is provided with HTTP status
+   * code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DEPOSIT_DB_DENOMINATION_KEY_UNKNOWN = 1203,
+  
+  /**
+   * The exchange database is unaware of the denomination key that
+   * signed the coin (however, the exchange process is; this is not
+   * supposed to happen; it can happen if someone decides to purge the
+   * DB behind the back of the exchange process).  Hence the deposit
+   * is being refused.  This response is provided with HTTP status
+   * code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_DEPOSIT_DENOMINATION_KEY_UNKNOWN = 1204,
+
+  /**
+   * The signature of the coin is not valid.  This response is
+   * provided with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_COIN_SIGNATURE_INVALID = 1205,
+
+  /**
+   * The signature of the denomination key over the coin is not valid.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_DENOMINATION_SIGNATURE_INVALID = 1206,
+
+  /**
+   * The stated value of the coin after the deposit fee is subtracted
+   * would be negative.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_NEGATIVE_VALUE_AFTER_FEE = 1207,
+
+  /**
+   * The stated refund deadline is after the wire deadline.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_REFUND_DEADLINE_AFTER_WIRE_DEADLINE = 1208,
+
+  /**
+   * The exchange does not recognize the validity of or support the
+   * given wire (bank account) address.  This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_INVALID_WIRE_FORMAT = 1209,
+
+  /**
+   * The exchange failed to canonicalize and hash the given wire format.
+   * This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_INVALID_WIRE_FORMAT_JSON = 1210,
+
+  /**
+   * The hash of the given wire address does not match the hash
+   * specified in the contract.
+   * This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_DEPOSIT_INVALID_WIRE_FORMAT_CONTRACT_HASH_CONFLICT = 1211,
+
+  /**
+   * The exchange failed to obtain the transaction history of the
+   * given coin from the database while generating an insufficient
+   * funds errors.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_DEPOSIT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS = 1212,
+  
+  /**
+   * The respective coin did not have sufficient residual value
+   * for the /refresh/melt operation.  The "history" in this
+   * response provdes the "residual_value" of the coin, which may
+   * be less than its "original_value".  This response is provided
+   * with HTTP status code MHD_HTTP_FORBIDDEN.
+   */
+  TALER_EC_REFRESH_MELT_INSUFFICIENT_FUNDS = 1300,
+
+  /**
+   * The exchange is unaware of the denomination key that was
+   * used to sign the melted coin.  This response is provided
+   * with HTTP status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_REFRESH_MELT_DENOMINATION_KEY_NOT_FOUND = 1301,
+
+  /**
+   * The exchange had an internal error reconstructing the
+   * transaction history of the coin that was being melted.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */ 
+  TALER_EC_REFRESH_MELT_COIN_HISTORY_COMPUTATION_FAILED = 1302,
+
+  /**
+   * The exchange failed to check against historic melt data from
+   * database (as part of ensuring the idempotency of the operation).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_DB_FETCH_ERROR = 1303,
+
+  /**
+   * The exchange failed to store session data in the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_DB_STORE_SESSION_ERROR = 1304,
+
+  /**
+   * The exchange failed to store refresh order data in the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_DB_STORE_ORDER_ERROR = 1305,
+
+  /**
+   * The exchange failed to store commit data in the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_DB_STORE_COMMIT_ERROR = 1306,
+  
+  /**
+   * The exchange failed to store transfer keys in the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_DB_STORE_TRANSFER_ERROR = 1307,
+
+  /**
+   * The exchange is unaware of the denomination key that was
+   * requested for one of the fresh coins.  This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_FRESH_DENOMINATION_KEY_NOT_FOUND = 1308,
+
+  /**
+   * The exchange encountered a numeric overflow totaling up
+   * the cost for the refresh operation.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_COST_CALCULATION_OVERFLOW = 1309,
+
+  /**
+   * During the transaction phase, the exchange could suddenly
+   * no longer find the denomination key that was
+   * used to sign the melted coin.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_DB_DENOMINATION_KEY_NOT_FOUND = 1310,
+
+  /**
+   * The exchange encountered melt fees exceeding the melted
+   * coin's contribution.  This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_FEES_EXCEED_CONTRIBUTION = 1311,
+
+  /**
+   * The exchange's cost calculation does not add up to the
+   * melt fees specified in the request.  This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_FEES_MISSMATCH = 1312,
+
+  /**
+   * The denomination key signature on the melted coin is invalid.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_DENOMINATION_SIGNATURE_INVALID = 1313,
+
+  /**
+   * The exchange's cost calculation shows that the melt amount
+   * is below the costs of the transaction.  This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_AMOUNT_INSUFFICIENT = 1314,
+
+  /**
+   * The signature made with the coin to be melted is invalid.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_COIN_SIGNATURE_INVALID = 1315,
+
+  /**
+   * The size of the cut-and-choose dimension of the 
+   * blinded coins request does not match #TALER_CNC_KAPPA.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_CNC_COIN_ARRAY_SIZE_INVALID = 1316,
+  
+  /**
+   * The size of the cut-and-choose dimension of the 
+   * transfer keys request does not match #TALER_CNC_KAPPA.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_MELT_CNC_TRANSFER_ARRAY_SIZE_INVALID = 1317,
+
+  /**
+   * The exchange failed to obtain the transaction history of the
+   * given coin from the database while generating an insufficient
+   * funds errors.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_REFRESH_MELT_HISTORY_DB_ERROR_INSUFFICIENT_FUNDS = 1318,
+  
+  /**
+   * The provided transfer keys do not match up with the
+   * original commitment.  Information about the original
+   * commitment is included in the response.  This response is
+   * provided with HTTP status code MHD_HTTP_CONFLICT.
+   */
+  TALER_EC_REFRESH_REVEAL_COMMITMENT_VIOLATION = 1350,
+
+  /**
+   * Failed to blind the envelope to reconstruct the blinded
+   * coins for revealation checks.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_REVEAL_BLINDING_ERROR = 1351,
+
+  /**
+   * Failed to produce the blinded signatures over the coins
+   * to be returned.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */ 
+  TALER_EC_REFRESH_REVEAL_SIGNING_ERROR = 1352,
+  
+  /**
+   * The exchange is unaware of the refresh sessino specified in
+   * the request.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST. 
+   */
+  TALER_EC_REFRESH_REVEAL_SESSION_UNKNOWN = 1353,
+
+  /**
+   * The exchange failed to retrieve valid session data from the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_REVEAL_DB_FETCH_SESSION_ERROR = 1354,
+
+  /**
+   * The exchange failed to retrieve order data from the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_REVEAL_DB_FETCH_ORDER_ERROR = 1355,
+
+  /**
+   * The exchange failed to retrieve transfer keys from the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_REVEAL_DB_FETCH_TRANSFER_ERROR = 1356,
+
+  /**
+   * The exchange failed to retrieve commitment data from the
+   * database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_ERROR.
+   */
+  TALER_EC_REFRESH_REVEAL_DB_FETCH_COMMIT_ERROR = 1357,
+
+  /**
+   * The size of the cut-and-choose dimension of the 
+   * private transfer keys request does not match #TALER_CNC_KAPPA - 1.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFRESH_REVEAL_CNC_TRANSFER_ARRAY_SIZE_INVALID = 1358,
+  
+  
+  /**
+   * The coin specified in the link request is unknown to the exchange.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_REFRESH_LINK_COIN_UNKNOWN = 1400,
+
+  
+  /**
+   * The exchange knows literally nothing about the coin we were asked
+   * to refund. But without a transaction history, we cannot issue a
+   * refund.  This is kind-of OK, the owner should just refresh it
+   * directly without executing the refund.  This response is provided
+   * with HTTP status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_REFUND_COIN_NOT_FOUND = 1500,
+
+  /**
+   * We could not process the refund request as the coin's transaction
+   * history does not permit the requested refund at this time.  The
+   * "history" in the response proves this.  This response is provided
+   * with HTTP status code MHD_HTTP_CONFLICT.
+   */
+  TALER_EC_REFUND_CONFLICT = 1501,
+  
+  /**
+   * The exchange knows about the coin we were asked to refund, but
+   * not about the specific /deposit operation.  Hence, we cannot
+   * issue a refund (as we do not know if this merchant public key is
+   * authorized to do a refund).  This response is provided with HTTP
+   * status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_REFUND_DEPOSIT_NOT_FOUND = 1503,
 
+  /**
+   * The currency specified for the refund is different from
+   * the currency of the coin.  This response is provided with HTTP
+   * status code MHD_HTTP_PRECONDITION_FAILED.
+   */
+  TALER_EC_REFUND_CURRENCY_MISSMATCH = 1504,
+
+  /**
+   * When we tried to check if we already paid out the coin, the
+   * exchange's database suddenly disagreed with data it previously
+   * provided (internal inconsistency).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_REFUND_DB_INCONSISTENT = 1505,
 
+  /**
+   * The exchange can no longer refund the customer/coin as the
+   * money was already transferred (paid out) to the merchant.
+   * (It should be past the refund deadline.)
+   * This response is provided with HTTP status code
+   * MHD_HTTP_GONE.
+   */
+  TALER_EC_REFUND_MERCHANT_ALREADY_PAID = 1506,
+
+  /**
+   * The amount the exchange was asked to refund exceeds
+   * (with fees) the total amount of the deposit (including fees).
+   * This response is provided with HTTP status code
+   * MHD_HTTP_PRECONDITION_FAILED.
+   */
+  TALER_EC_REFUND_INSUFFICIENT_FUNDS = 1507,
+
+  /**
+   * The exchange failed to recover information about the
+   * denomination key of the refunded coin (even though it
+   * recognizes the key).  Hence it could not check the fee
+   * strucutre.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_REFUND_DENOMINATION_KEY_NOT_FOUND = 1508,
+
+  /**
+   * The refund fee specified for the request is lower than
+   * the refund fee charged by the exchange for the given 
+   * denomination key of the refunded coin.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFUND_FEE_TOO_LOW = 1509,
+
+  /**
+   * The exchange failed to store the refund information to
+   * its database.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_REFUND_STORE_DB_ERROR = 1510,
+
+  /**
+   * The refund fee is specified in a different currency
+   * than the refund amount.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFUND_FEE_CURRENCY_MISSMATCH = 1511,
+
+  /**
+   * The refunded amount is smaller than the refund fee,
+   * which would result in a negative refund.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFUND_FEE_ABOVE_AMOUNT = 1512,
+
+  /**
+   * The signature of the merchant is invalid.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_REFUND_MERCHANT_SIGNATURE_INVALID = 1513,
+
+  
+  /**
+   * The wire format specified in the "sender_account_details"
+   * is not understood or not supported by this exchange.
+   * Returned with an HTTP status code of MHD_HTTP_NOT_FOUND.
+   * (As we did not find an interpretation of the wire format.)
+   */
+  TALER_EC_ADMIN_ADD_INCOMING_WIREFORMAT_UNSUPPORTED = 1600,
+
+  /**
+   * The currency specified in the "amount" parameter is not
+   * supported by this exhange.  Returned with an HTTP status
+   * code of MHD_HTTP_BAD_REQUEST.
+   */ 
+  TALER_EC_ADMIN_ADD_INCOMING_CURRENCY_UNSUPPORTED = 1601,
+
+  /**
+   * The exchange failed to store information about the incoming
+   * transfer in its database.  This response is provided with HTTP
+   * status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_ADMIN_ADD_INCOMING_DB_STORE = 1602,
+
+  /**
+   * The exchange encountered an error (that is not about not finding
+   * the wire transfer) trying to lookup a wire transfer identifier
+   * in the database.  This response is provided with HTTP
+   * status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TRACK_TRANSFER_DB_FETCH_FAILED = 1700,
+
+  /**
+   * The exchange found internally inconsistent data when resolving a
+   * wire transfer identifier in the database.  This response is
+   * provided with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TRACK_TRANSFER_DB_INCONSISTENT = 1701,
+
+  /**
+   * The exchange did not find information about the specified
+   * wire transfer identifier in the database.  This response is
+   * provided with HTTP status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_TRACK_TRANSFER_WTID_NOT_FOUND = 1702,
+
+  
+  /**
+   * The exchange found internally inconsistent fee data when
+   * resolving a transaction in the database.  This
+   * response is provided with HTTP status code
+   * MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TRACK_TRANSACTION_DB_FEE_INCONSISTENT = 1800,
+
+  /**
+   * The exchange encountered an error (that is not about not finding
+   * the transaction) trying to lookup a transaction 
+   * in the database.  This response is provided with HTTP
+   * status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TRACK_TRANSACTION_DB_FETCH_FAILED = 1801,
+
+  /**
+   * The exchange did not find information about the specified
+   * transaction in the database.  This response is
+   * provided with HTTP status code MHD_HTTP_NOT_FOUND.
+   */
+  TALER_EC_TRACK_TRANSACTION_NOT_FOUND = 1802,
+  
+  /**
+   * The exchange failed to identify the wire transfer of the
+   * transaction (or information about the plan that it was supposed
+   * to still happen in the future).  This response is provided with
+   * HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TRACK_TRANSACTION_WTID_RESOLUTION_ERROR = 1803,
+
+  /**
+   * The signature of the merchant is invalid.
+   * This response is provided with HTTP status code
+   * MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_TRACK_TRANSACTION_MERCHANT_SIGNATURE_INVALID = 1804,
+
+  
+  /* ********** /test API error codes ************* */
+  
+  /**
+   * The exchange failed to compute ECDH.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TEST_ECDH_ERROR = 4000,
+
+  /**
+   * The EdDSA test signature is invalid.  This response is provided
+   * with HTTP status code MHD_HTTP_BAD_REQUEST.
+   */
+  TALER_EC_TEST_EDDSA_INVALID = 4001,
+
+  /**
+   * The exchange failed to compute the EdDSA test signature.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TEST_EDDSA_ERROR = 4002,
+
+  /**
+   * The exchange failed to generate an RSA key.  This response is provided
+   * with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TEST_RSA_GEN_ERROR = 4003,
+
+  /**
+   * The exchange failed to compute the public RSA key.  This response
+   * is provided with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TEST_RSA_PUB_ERROR = 4004,
+
+  /**
+   * The exchange failed to compute the RSA signature.  This response
+   * is provided with HTTP status code MHD_HTTP_INTERNAL_SERVER_ERROR.
+   */
+  TALER_EC_TEST_RSA_SIGN_ERROR = 4005,
+
+  
+  /**
+   * End of error code range.
+   */
+  TALER_EC_END = 9999
+  
 };