diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -580,6 +580,7 @@
   platformDetails: tPlatformDetails,
   watchedIDs: t.list(tID),
   signedIdentityKeysBlob: t.maybe(signedIdentityKeysBlobValidator),
+  initialNotificationsEncryptedMessage: t.maybe(t.String),
 });
 
 async function siweAuthResponder(
@@ -598,6 +599,7 @@
     deviceTokenUpdateRequest,
     platformDetails,
     signedIdentityKeysBlob,
+    initialNotificationsEncryptedMessage,
   } = request;
   const calendarQuery = normalizeCalendarQuery(request.calendarQuery);
 
@@ -708,6 +710,7 @@
     calendarQuery,
     socialProof,
     signedIdentityKeysBlob,
+    initialNotificationsEncryptedMessage,
   });
   return validateOutput(
     viewer.platformDetails,
diff --git a/lib/types/siwe-types.js b/lib/types/siwe-types.js
--- a/lib/types/siwe-types.js
+++ b/lib/types/siwe-types.js
@@ -20,6 +20,7 @@
   +platformDetails: PlatformDetails,
   +watchedIDs: $ReadOnlyArray<string>,
   +signedIdentityKeysBlob?: ?SignedIdentityKeysBlob,
+  +initialNotificationsEncryptedMessage?: string,
 };
 
 export type SIWEAuthServerCall = {
diff --git a/native/account/siwe-hooks.js b/native/account/siwe-hooks.js
--- a/native/account/siwe-hooks.js
+++ b/native/account/siwe-hooks.js
@@ -12,6 +12,7 @@
 import { NavContext } from '../navigation/navigation-context.js';
 import { useSelector } from '../redux/redux-utils.js';
 import { nativeLogInExtraInfoSelector } from '../selectors/account-selectors.js';
+import { useInitialNotificationsEncryptedMessage } from '../utils/crypto-utils.js';
 
 type SIWEServerCallParams = {
   +message: string,
@@ -52,19 +53,32 @@
     }),
   );
 
+  const getInitialNotificationsEncryptedMessage =
+    useInitialNotificationsEncryptedMessage();
+
   const dispatchActionPromise = useDispatchActionPromise();
   return React.useCallback(
     async ({ message, signature }) => {
       const extraInfo = await logInExtraInfo();
+      const initialNotificationsEncryptedMessage =
+        await getInitialNotificationsEncryptedMessage();
 
       dispatchActionPromise(
         siweAuthActionTypes,
-        callSIWE(message, signature, extraInfo),
+        callSIWE(message, signature, {
+          ...extraInfo,
+          initialNotificationsEncryptedMessage,
+        }),
         undefined,
         ({ calendarQuery: extraInfo.calendarQuery }: LogInStartingPayload),
       );
     },
-    [logInExtraInfo, dispatchActionPromise, callSIWE],
+    [
+      logInExtraInfo,
+      dispatchActionPromise,
+      callSIWE,
+      getInitialNotificationsEncryptedMessage,
+    ],
   );
 }