diff --git a/backend/src/matrix.js b/backend/src/matrix.js
index 3ae7401..e7b615b 100644
--- a/backend/src/matrix.js
+++ b/backend/src/matrix.js
@@ -67,7 +67,7 @@ const start = async () => {
     // Leave targetRoomId uninitialized for now
   }
 
-  async function handleCommand(roomId, event) {
+  const handleCommand = async (roomId, event) => {
     // Don't handle unhelpful events (ones that aren't text messages, are redacted, or sent by us)
     if (event.content?.msgtype !== 'm.text') return;
     if (event.sender === await client.getUserId()) return;
@@ -101,11 +101,29 @@ const start = async () => {
         // Not found
       }
     }
-  }
+  };
+
+  const handleRegisterIdentity = async (roomId, event) => {
+    // const { message, signature } = event.content;
+    await client.replyNotice(roomId, event, 'Received request to register identity');
+  };
 
   // Before we start the bot, register our command handler
   client.on('room.message', handleCommand);
 
+  // Handler for custom events
+  client.on('room.event', (roomId, event) => {
+    // Note that state events can also be sent down this listener too
+    if (event.state_key !== undefined) return; // state event
+
+    switch (event.type) {
+      case 'io.dgov.identity.register':
+        handleRegisterIdentity(roomId, event);
+        break;
+      default:
+    }
+  });
+
   client.start().then(() => {
     console.log('Bot started!');
     outboundQueue.resume();
diff --git a/frontend/src/Widget.jsx b/frontend/src/Widget.jsx
index 7b8ccd7..c1733d5 100644
--- a/frontend/src/Widget.jsx
+++ b/frontend/src/Widget.jsx
@@ -368,13 +368,20 @@ function Widget() {
     setShowViewPost(true);
   }, [setViewPost, setShowViewPost]);
 
-  // TODO: Sign and send a message to the forum-api bot / to a room in matrix
-  const registerMatrixIdentity = async () => {
-    await widgetApi.current.sendRoomEvent('m.room.message', {
-      body: 'test message',
-      msgtype: 'm.text',
+  const registerMatrixIdentity = useCallback(async () => {
+    const message = new Date().toISOString();
+
+    const signature = await provider.request({
+      method: 'personal_sign',
+      params: [message, account],
     });
-  };
+
+    // TODO: Sign and send a message
+    await widgetApi.current.sendRoomEvent('io.dgov.identity.register', {
+      message,
+      signature,
+    });
+  }, [provider, account]);
 
   /* -------------------------------------------------------------------------------- */
   /* --------------------------- END UI ACTIONS ------------------------------------- */