diff --git a/callback_dispatcher.hh b/callback_dispatcher.hh
index 17f39e3..079e56e 100644
--- a/callback_dispatcher.hh
+++ b/callback_dispatcher.hh
@@ -5,9 +5,10 @@
 #include <mutex>
 #include "Adapter.hh"
 #include "Semaphore.hh"
-#include "passphrase_cache.hh"
 
 namespace pEp {
+    class PassphraseCache;
+
     // use this class when implementing a desktop adapter
     // register different interfaces with add()
     // then use CallbackDispatcher::start_sync() to start Sync
@@ -48,7 +49,7 @@ namespace pEp {
         PEP_STATUS _notifyHandshake(::pEp_identity *me,
                 ::pEp_identity *partner, ::sync_handshake_signal signal);
 
-        friend const char *PassphraseCache::add(const std::string& passphrase);
+        friend class PassphraseCache;
     };
 
     extern CallbackDispatcher callback_dispatcher;
diff --git a/passphrase_cache.cc b/passphrase_cache.cc
index 45e10b1..6112850 100644
--- a/passphrase_cache.cc
+++ b/passphrase_cache.cc
@@ -1,9 +1,6 @@
 #include <cassert>
 #include "Adapter.hh"
 #include "passphrase_cache.hh"
-#include "callback_dispatcher.hh"
-
-pEp::PassphraseCache pEp::passphrase_cache;
 
 namespace pEp {
     PassphraseCache::cache_entry::cache_entry(const std::string& p, time_point t) :
@@ -12,13 +9,13 @@ namespace pEp {
 
     PassphraseCache::PassphraseCache(size_t max_size, duration timeout) :
             _max_size{max_size}, _timeout{timeout}, _which(_cache.end()),
-            first_time(true)
+            first_time(true), synchronous(false)
     { }
 
     PassphraseCache::PassphraseCache(const PassphraseCache& second) :
             _cache{second._cache}, _max_size{second._max_size},
             _timeout{second._timeout}, _stored{second._stored},
-            _which(_cache.end()), first_time(true)
+            _which(_cache.end()), first_time(true), synchronous(false)
     {
         cleanup();
     }
diff --git a/passphrase_cache.hh b/passphrase_cache.hh
index 205d1ea..8bb4625 100644
--- a/passphrase_cache.hh
+++ b/passphrase_cache.hh
@@ -8,6 +8,8 @@
 #include <exception>
 #include <pEp/message_api.h>
 
+#include "callback_dispatcher.hh"
+
 namespace pEp {
     class PassphraseCache {
         using clock = std::chrono::system_clock;
@@ -33,6 +35,8 @@ namespace pEp {
         cache::iterator _which;
         bool first_time;
 
+        bool synchronous;
+
     public:
         struct Empty : public std::underflow_error {
             Empty() : std::underflow_error("passphrase cache empty") { }
@@ -46,6 +50,9 @@ namespace pEp {
         PassphraseCache(const PassphraseCache& second);
         PassphraseCache& operator=(const PassphraseCache& second);
 
+        // switch this on for synchronous API
+        void config_synchronous_api(bool enable = true) { synchronous = enable; }
+
         // adds the passphrase to the cache, which will timeout
         // returns a ptr to the passsword entry in the cache. Don't free() it!
         const char *add(const std::string& passphrase);
diff --git a/passphrase_cache.hxx b/passphrase_cache.hxx
index 17d9288..2af3750 100644
--- a/passphrase_cache.hxx
+++ b/passphrase_cache.hxx
@@ -1,21 +1,33 @@
-#pragma once
 #include "passphrase_cache.hh"
 
+extern pEp::CallbackDispatcher callback_dispatcher;
+
 namespace pEp {
     template<typename... A> PEP_STATUS PassphraseCache::api(
             PEP_STATUS f(PEP_SESSION, A...), PEP_SESSION session, A... a)
     {
         PEP_STATUS status;
 
-        for_each_passphrase([&](std::string passphrase) {
-            status = ::config_passphrase(session, passphrase.c_str());
-            if (status)
-                return true;
+        do {
+            if (synchronous) {
+                callback_dispatcher.semaphore.try_wait();
+            }
+
+            for_each_passphrase([&](std::string passphrase) {
+                status = ::config_passphrase(session, passphrase.c_str());
+                if (status)
+                    return true;
+
+                status = f(session, a...);
+                return status != PEP_PASSPHRASE_REQUIRED &&
+                        status != PEP_WRONG_PASSPHRASE;
+            });
 
-            status = f(session, a...);
-            return status != PEP_PASSPHRASE_REQUIRED &&
-                    status != PEP_WRONG_PASSPHRASE;
-        });
+            if (synchronous) {
+                CallbackDispatcher::notifyHandshake(nullptr, nullptr, SYNC_PASSPHRASE_REQUIRED);
+                callback_dispatcher.semaphore.stop();
+            }
+        } while (synchronous);
 
         return status;
     }