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
@@ -193,4 +193,144 @@
   };
 }
 
-export default createAccount;
+async function createSIWEAccount(
+  viewer: Viewer,
+  request: RegisterRequest,
+): Promise<RegisterResponse> {
+  if (request.password.trim() === '') {
+    throw new ServerError('empty_password');
+  }
+  const usernameRegex = hasMinCodeVersion(viewer.platformDetails, 69)
+    ? validUsernameRegex
+    : oldValidUsernameRegex;
+  if (request.username.search(usernameRegex) === -1) {
+    throw new ServerError('invalid_username');
+  }
+
+  const usernameQuery = SQL`
+    SELECT COUNT(id) AS count
+    FROM users
+    WHERE LCASE(username) = LCASE(${request.username})
+  `;
+  const promises = [dbQuery(usernameQuery)];
+  const { calendarQuery } = request;
+  if (calendarQuery) {
+    promises.push(verifyCalendarQueryThreadIDs(calendarQuery));
+  }
+
+  const [[usernameResult]] = await Promise.all(promises);
+  if (reservedUsernamesSet.has(request.username.toLowerCase())) {
+    if (hasMinCodeVersion(viewer.platformDetails, 120)) {
+      throw new ServerError('username_reserved');
+    } else {
+      throw new ServerError('username_taken');
+    }
+  }
+  if (usernameResult[0].count !== 0) {
+    throw new ServerError('username_taken');
+  }
+
+  const hash = bcrypt.hashSync(request.password);
+  const time = Date.now();
+  const deviceToken = request.deviceTokenUpdateRequest
+    ? request.deviceTokenUpdateRequest.deviceToken
+    : viewer.deviceToken;
+  const [id] = await createIDs('users', 1);
+  const newUserRow = [id, request.username, hash, time];
+  const newUserQuery = SQL`
+    INSERT INTO users(id, username, hash, creation_time)
+    VALUES ${[newUserRow]}
+  `;
+  const [userViewerData] = await Promise.all([
+    createNewUserCookie(id, {
+      platformDetails: request.platformDetails,
+      deviceToken,
+    }),
+    deleteCookie(viewer.cookieID),
+    dbQuery(newUserQuery),
+  ]);
+  viewer.setNewCookie(userViewerData);
+
+  if (calendarQuery) {
+    await setNewSession(viewer, calendarQuery, 0);
+  }
+
+  await Promise.all([
+    updateThread(
+      createScriptViewer(ashoat.id),
+      {
+        threadID: genesis.id,
+        changes: { newMemberIDs: [id] },
+      },
+      { forceAddMembers: true, silenceMessages: true, ignorePermissions: true },
+    ),
+    viewerAcknowledgmentUpdater(viewer, policyTypes.tosAndPrivacyPolicy),
+  ]);
+
+  const [privateThreadResult, ashoatThreadResult] = await Promise.all([
+    createPrivateThread(viewer, request.username),
+    createThread(
+      viewer,
+      {
+        type: threadTypes.PERSONAL,
+        initialMemberIDs: [ashoat.id],
+      },
+      { forceAddMembers: true },
+    ),
+  ]);
+  const ashoatThreadID = ashoatThreadResult.newThreadInfo
+    ? ashoatThreadResult.newThreadInfo.id
+    : ashoatThreadResult.newThreadID;
+  const privateThreadID = privateThreadResult.newThreadInfo
+    ? privateThreadResult.newThreadInfo.id
+    : privateThreadResult.newThreadID;
+  invariant(
+    ashoatThreadID && privateThreadID,
+    'createThread should return either newThreadInfo or newThreadID',
+  );
+
+  let messageTime = Date.now();
+  const ashoatMessageDatas = ashoatMessages.map(message => ({
+    type: messageTypes.TEXT,
+    threadID: ashoatThreadID,
+    creatorID: ashoat.id,
+    time: messageTime++,
+    text: message,
+  }));
+  const privateMessageDatas = privateMessages.map(message => ({
+    type: messageTypes.TEXT,
+    threadID: privateThreadID,
+    creatorID: commbot.userID,
+    time: messageTime++,
+    text: message,
+  }));
+  const messageDatas = [...ashoatMessageDatas, ...privateMessageDatas];
+  const [
+    messageInfos,
+    threadsResult,
+    userInfos,
+    currentUserInfo,
+  ] = await Promise.all([
+    createMessages(viewer, messageDatas),
+    fetchThreadInfos(viewer),
+    fetchKnownUserInfos(viewer),
+    fetchLoggedInUserInfo(viewer),
+  ]);
+  const rawMessageInfos = [
+    ...ashoatThreadResult.newMessageInfos,
+    ...privateThreadResult.newMessageInfos,
+    ...messageInfos,
+  ];
+
+  return {
+    id,
+    rawMessageInfos,
+    currentUserInfo,
+    cookieChange: {
+      threadInfos: threadsResult.threadInfos,
+      userInfos: values(userInfos),
+    },
+  };
+}
+
+export { createAccount, createSIWEAccount };
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
@@ -44,7 +44,7 @@
   tOldValidUsername,
 } from 'lib/utils/validation-utils';
 
-import createAccount from '../creators/account-creator';
+import { createAccount } from '../creators/account-creator';
 import { dbQuery, SQL } from '../database/database';
 import { deleteAccount } from '../deleters/account-deleters';
 import { deleteCookie } from '../deleters/cookie-deleters';