diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index bc57ac4..7bde60d 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,27 @@
+2018-04-27  Yacine Bandou  <yacine.bandou_ext@softathome.com>
+
+        [EME][GStreamer] Add a new message "decrypt-key-needed" send from the decryptor to the application.
+        https://bugs.webkit.org/show_bug.cgi?id=181858
+
+        Reviewed by Xabier Rodriguez-Calvar.
+
+        Add a new message "decrypt-key-needed" that the decryptor can send when it doesn't have an available key.
+        This message should be handled by the application in order to dispatch or send the key to the decryptor.
+        This patch is a preparation for the patch 181855.
+        With the patch 181855, the decryptor will be in the PlaybackPipeline instead of AppendPipeline, thus we can
+        get the DRM license or key before to instantiate or load the decryptor plugin in PlaybackPipeline.
+        When the decryptor plugin is instantiated or loaded, it should able to ask the application to resend
+        the DRM license or key by using this new message "decrypt-key-needed".
+
+
+        * platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
+        (WebCore::MediaPlayerPrivateGStreamer::handleMessage):
+        * platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.cpp:
+        (WebCore::MediaPlayerPrivateGStreamerBase::dispatchCDMInstance):
+        * platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.h:
+        * platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp:
+        (webkitMediaCommonEncryptionDecryptTransformInPlace):
+
 2018-04-26  Justin Fan  <justin_fan@apple.com>
 
         tex[Sub]Image2D slow when passing in a <canvas>, faster with ImageData.
diff --git a/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp b/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp
index 784c961..36a9526 100644
--- a/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp
@@ -1245,6 +1245,9 @@
             GRefPtr<GstEvent> event;
             gst_structure_get(structure, "event", GST_TYPE_EVENT, &event.outPtr(), nullptr);
             handleProtectionEvent(event.get());
+        } else if (gst_structure_has_name(structure, "decrypt-key-needed")) {
+            GST_DEBUG("decrypt-key-needed message from %s", GST_MESSAGE_SRC_NAME(message));
+            MediaPlayerPrivateGStreamerBase::dispatchCDMInstance();
         }
 #endif
         else if (gst_structure_has_name(structure, "http-headers")) {
diff --git a/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.cpp b/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.cpp
index 8e476ff..1557475 100644
--- a/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.cpp
@@ -1244,6 +1244,13 @@
     GST_TRACE("emitted decryption cipher key on pipeline, event handled %s, need to resend credentials %s", boolForPrinting(eventHandled), boolForPrinting(m_needToResendCredentials));
 }
 
+void MediaPlayerPrivateGStreamerBase::dispatchCDMInstance()
+{
+    // This function dispatches the CDMInstance in GStreamer playback pipeline.
+    if (m_cdmInstance)
+        m_player->attemptToDecryptWithInstance(const_cast<CDMInstance&>(*m_cdmInstance.get()));
+}
+
 void MediaPlayerPrivateGStreamerBase::handleProtectionEvent(GstEvent* event)
 {
     if (m_handledProtectionEvents.contains(GST_EVENT_SEQNUM(event))) {
diff --git a/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.h b/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.h
index 8e8db7f..64ffb8d 100644
--- a/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.h
+++ b/Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamerBase.h
@@ -143,6 +143,7 @@
     void handleProtectionEvent(GstEvent*);
     void attemptToDecryptWithLocalInstance();
     void attemptToDecryptWithInstance(CDMInstance&) override;
+    void dispatchCDMInstance();
 #endif
 
     static bool supportsKeySystem(const String& keySystem, const String& mimeType);
diff --git a/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp b/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp
index f420af9..33a330a 100644
--- a/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp
+++ b/Source/WebCore/platform/graphics/gstreamer/eme/WebKitCommonEncryptionDecryptorGStreamer.cpp
@@ -197,6 +197,9 @@
             GST_ERROR_OBJECT(self, "can't process key requests in less than PAUSED state");
             return GST_FLOW_NOT_SUPPORTED;
         }
+        // Send "decrypt-key-needed" message to the application in order to resend the key if it is available in the application.
+        gst_element_post_message(GST_ELEMENT(self), gst_message_new_element(GST_OBJECT(self), gst_structure_new_empty("decrypt-key-needed")));
+
         priv->condition.waitFor(priv->mutex, Seconds(5), [priv] {
             return priv->keyReceived;
         });