diff --git a/Stellar-contract.x b/Stellar-contract.x
index 2921c93..6a0bc7a 100644
--- a/Stellar-contract.x
+++ b/Stellar-contract.x
@@ -78,7 +78,8 @@ enum SCStatusType
     SST_HOST_STORAGE_ERROR = 5,
     SST_HOST_CONTEXT_ERROR = 6,
     SST_VM_ERROR = 7,
-    SST_CONTRACT_ERROR = 8
+    SST_CONTRACT_ERROR = 8,
+    SST_HOST_AUTH_ERROR = 9
     // TODO: add more
 };
 
@@ -128,6 +129,14 @@ enum SCHostStorageErrorCode
     HOST_STORAGE_GET_ON_DELETED_KEY = 5
 };
 
+enum SCHostAuthErrorCode
+{
+    HOST_AUTH_UNKNOWN_ERROR = 0,
+    HOST_AUTH_NONCE_ERROR = 1,
+    HOST_AUTH_DUPLICATE_AUTHORIZATION = 2,
+    HOST_AUTH_NOT_AUTHORIZED = 3
+};
+
 enum SCHostContextErrorCode
 {
     HOST_CONTEXT_UNKNOWN_ERROR = 0,
@@ -182,6 +191,8 @@ case SST_VM_ERROR:
     SCVmErrorCode vmCode;
 case SST_CONTRACT_ERROR:
     uint32 contractCode;
+case SST_HOST_AUTH_ERROR:
+    SCHostAuthErrorCode authCode;
 };
 
 union SCVal switch (SCValType type)