diff --git a/keyserver/src/creators/account-creator.js b/keyserver/src/creators/account-creator.js
--- a/keyserver/src/creators/account-creator.js
+++ b/keyserver/src/creators/account-creator.js
@@ -1,6 +1,7 @@
 // @flow
 
 import invariant from 'invariant';
+import { getRustAPI } from 'rust-node-addon';
 import bcrypt from 'twin-bcrypt';
 
 import ashoat from 'lib/facts/ashoat.js';
@@ -16,7 +17,10 @@
   RegisterResponse,
   RegisterRequest,
 } from 'lib/types/account-types.js';
-import type { SignedIdentityKeysBlob } from 'lib/types/crypto-types.js';
+import type {
+  SignedIdentityKeysBlob,
+  IdentityKeysBlob,
+} from 'lib/types/crypto-types.js';
 import type {
   PlatformDetails,
   DeviceTokenUpdateRequest,
@@ -45,6 +49,7 @@
   fetchKnownUserInfos,
 } from '../fetchers/user-fetchers.js';
 import { verifyCalendarQueryThreadIDs } from '../responders/entry-responders.js';
+import { handleAsyncPromise } from '../responders/handlers.js';
 import { createNewUserCookie, setNewSession } from '../session/cookies.js';
 import { createScriptViewer } from '../session/scripts.js';
 import type { Viewer } from '../session/viewer.js';
@@ -81,7 +86,7 @@
     WHERE LCASE(username) = LCASE(${request.username})
   `;
   const promises = [dbQuery(usernameQuery)];
-  const { calendarQuery } = request;
+  const { calendarQuery, signedIdentityKeysBlob } = request;
   if (calendarQuery) {
     promises.push(verifyCalendarQueryThreadIDs(calendarQuery));
   }
@@ -113,12 +118,13 @@
     VALUES ${[newUserRow]}
   `;
 
-  const [userViewerData] = await Promise.all([
+  const [userViewerData, rustAPI] = await Promise.all([
     createNewUserCookie(id, {
       platformDetails: request.platformDetails,
       deviceToken,
-      signedIdentityKeysBlob: request.signedIdentityKeysBlob,
+      signedIdentityKeysBlob,
     }),
+    getRustAPI(),
     deleteCookie(viewer.cookieID),
     dbQuery(newUserQuery),
   ]);
@@ -191,6 +197,22 @@
     ...messageInfos,
   ];
 
+  if (signedIdentityKeysBlob) {
+    const identityKeys: IdentityKeysBlob = JSON.parse(
+      signedIdentityKeysBlob.payload,
+    );
+
+    handleAsyncPromise(
+      rustAPI.registerUser(
+        id,
+        identityKeys.primaryIdentityPublicKeys.ed25519,
+        request.username,
+        request.password,
+        signedIdentityKeysBlob,
+      ),
+    );
+  }
+
   return {
     id,
     rawMessageInfos,
diff --git a/lib/types/rust-binding-types.js b/lib/types/rust-binding-types.js
--- a/lib/types/rust-binding-types.js
+++ b/lib/types/rust-binding-types.js
@@ -18,10 +18,10 @@
 type RustNativeBindingAPI = {
   +registerUser: (
     userId: string,
-    deviceId: string,
+    signingPublicKey: string,
     username: string,
     password: string,
-    userPublicKey: string,
+    sessionInitializationInfo: SignedIdentityKeysBlob,
   ) => Promise<string>,
   +loginUserPake: (
     userId: string,