diff --git a/src/basic_api.cc b/src/basic_api.cc
index b2be618..e713da0 100644
--- a/src/basic_api.cc
+++ b/src/basic_api.cc
@@ -6,6 +6,8 @@ namespace pEp {
     namespace PythonAdapter {
         void update_identity(Identity& ident)
         {
+            if (ident.address() == "")
+                throw invalid_argument("address needed");
             if (ident.me())
                 throw runtime_error("update_identity: not for own identities");
             if (ident.user_id() == PEP_OWN_USERID)
@@ -18,12 +20,49 @@ namespace pEp {
 
         void myself(Identity& ident)
         {
+            if (ident.address() == "")
+                throw invalid_argument("address needed");
+            if (ident.username() == "")
+                throw invalid_argument("username needed");
+            if (!(ident.user_id() == "" || ident.user_id() == PEP_OWN_USERID))
+                throw invalid_argument("user_id must be empty or '" PEP_OWN_USERID "'");
+
             ident.me(true);
             ident.user_id(PEP_OWN_USERID);
 
             PEP_STATUS status = myself(session, ident);
             _throw_status(status);
         }
+
+        string _trustwords(Identity me, Identity partner, string lang)
+        {
+            if (me.fpr() == "" || partner.fpr() == "")
+                throw invalid_argument("fingerprint needed in Identities");
+
+            if (lang == "" && me.lang() == partner.lang())
+                lang = me.lang();
+
+            char *words = NULL;
+            size_t size = 0;
+            PEP_STATUS status = trustwords(session, me.fpr().c_str(),
+                    lang.c_str(), &words, &size, 5);
+            _throw_status(status);
+            string my_words = words;
+
+            free(words);
+            words = NULL;
+            size = 0;
+            status = trustwords(session, partner.fpr().c_str(), lang.c_str(),
+                    &words, &size, 5);
+            _throw_status(status);
+            string partner_words = words;
+            free(words);
+
+            if (me.fpr() > partner.fpr())
+                return partner_words + my_words;
+            else
+                return my_words + partner_words;
+        }
     }
 }
 
diff --git a/src/basic_api.hh b/src/basic_api.hh
index b6bd1ae..ca4b33f 100644
--- a/src/basic_api.hh
+++ b/src/basic_api.hh
@@ -6,6 +6,7 @@ namespace pEp {
     namespace PythonAdapter {
         void update_identity(Identity& ident);
         void myself(Identity& ident);
+        string _trustwords(Identity me, Identity partner, string lang);
     }
 }
 
diff --git a/src/pEpmodule.cc b/src/pEpmodule.cc
index 9f53c5b..6725b94 100644
--- a/src/pEpmodule.cc
+++ b/src/pEpmodule.cc
@@ -196,6 +196,7 @@ BOOST_PYTHON_MODULE(pEp)
     // message API
 
     def("color", &_color, "calculate color value out of rating");
+    def("trustwords", &_trustwords, "calculate trustwords for two Identities");
 
     // key sync API