diff --git a/src/git.xdrm.io/schastsp/server/server.go b/src/git.xdrm.io/schastsp/server/server.go
index 7e79c17..d0aa236 100644
--- a/src/git.xdrm.io/schastsp/server/server.go
+++ b/src/git.xdrm.io/schastsp/server/server.go
@@ -1,6 +1,7 @@
 package server
 
 import (
+	"fmt"
 	"git.xdrm.io/schastsp/pkg/scha"
 	"io"
 	"os"
@@ -135,4 +136,30 @@ func (s *T) HandleRequest(req io.Reader, res io.Writer) error {
 	if written != len(y1) { return errors.New("Cannot write y2") }
 
 	return nil
+}
+
+
+
+/* (4) Apply a synchronisation key
+*
+* @syncKey<[]byte>					Synchronisation key from client
+*
+* @return err<error>
+*
+---------------------------------------------------------*/
+func (s *T) SynchronisationKey(syncKey []byte) error {
+
+	/* (1) Check size */
+	if uint16(len(syncKey)) != scha.HSIZE {
+		return fmt.Errorf("Invalid synchronisation key size (%d), expected %d bytes", len(syncKey), scha.HSIZE)
+	}
+
+	/* (2) Copy synchronisation key */
+	copy(s.hash, syncKey)
+
+	/* (3) Store new config */
+	s.store()
+
+	return nil
+
 }
\ No newline at end of file