diff --git a/keyserver/src/cron/cron.js b/keyserver/src/cron/cron.js
index 2b83481e33..6540ed0afc 100644
--- a/keyserver/src/cron/cron.js
+++ b/keyserver/src/cron/cron.js
@@ -6,6 +6,7 @@ import schedule from 'node-schedule';
 import { backupDB } from './backups.js';
 import { createDailyUpdatesThread } from './daily-updates.js';
 import { updateAndReloadGeoipDB } from './update-geoip-db.js';
+import { updateIdentityReservedUsernames } from './update-identity-reserved-usernames.js';
 import { deleteOrphanedActivity } from '../deleters/activity-deleters.js';
 import { deleteExpiredCookies } from '../deleters/cookie-deleters.js';
 import { deleteOrphanedDays } from '../deleters/day-deleters.js';
@@ -92,7 +93,20 @@ if (cluster.isMaster) {
       }
     },
   );
-
+  schedule.scheduleJob(
+    '0 5 * * *', // every day at 5:00 AM in the keyserver's timezone
+    async () => {
+      try {
+        await updateIdentityReservedUsernames();
+      } catch (e) {
+        console.warn(
+          'encountered error while trying to update reserved usernames on ' +
+            'identity service',
+          e,
+        );
+      }
+    },
+  );
   schedule.scheduleJob(
     '0 0 * * *', // every day at midnight in the keyserver's timezone
     async () => {
diff --git a/keyserver/src/cron/update-identity-reserved-usernames.js b/keyserver/src/cron/update-identity-reserved-usernames.js
new file mode 100644
index 0000000000..dfdd15aa4a
--- /dev/null
+++ b/keyserver/src/cron/update-identity-reserved-usernames.js
@@ -0,0 +1,28 @@
+// @flow
+
+import { getRustAPI } from 'rust-node-addon';
+
+import type { ReservedUsernameMessage } from 'lib/types/crypto-types.js';
+
+import { fetchAllUsernames } from '../fetchers/user-fetchers.js';
+import { fetchOlmAccount } from '../updaters/olm-account-updater.js';
+
+async function updateIdentityReservedUsernames(): Promise<void> {
+  const [usernames, rustAPI, accountInfo] = await Promise.all([
+    fetchAllUsernames(),
+    getRustAPI(),
+    fetchOlmAccount('content'),
+  ]);
+  const issuedAt = new Date().toISOString();
+  const reservedUsernameMessage: ReservedUsernameMessage = {
+    statement: 'Add the following usernames to reserved list',
+    payload: usernames,
+    issuedAt,
+  };
+  const stringifiedMessage = JSON.stringify(reservedUsernameMessage);
+  const signature = accountInfo.account.sign(stringifiedMessage);
+
+  await rustAPI.addReservedUsernames(stringifiedMessage, signature);
+}
+
+export { updateIdentityReservedUsernames };