diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
index e19b6e660..07c1be5d5 100644
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -1,666 +1,672 @@
 // @flow
 
 import invariant from 'invariant';
 import { getRustAPI } from 'rust-node-addon';
 import { ErrorTypes, SiweMessage } from 'siwe';
 import t from 'tcomb';
 import bcrypt from 'twin-bcrypt';
 
 import { baseLegalPolicies, policies } from 'lib/facts/policies.js';
 import { hasMinCodeVersion } from 'lib/shared/version-utils.js';
 import type {
   ResetPasswordRequest,
   LogOutResponse,
   DeleteAccountRequest,
   RegisterResponse,
   RegisterRequest,
   LogInResponse,
   LogInRequest,
   UpdatePasswordRequest,
   UpdateUserSettingsRequest,
   PolicyAcknowledgmentRequest,
 } from 'lib/types/account-types.js';
 import {
   userSettingsTypes,
   notificationTypeValues,
   logInActionSources,
 } from 'lib/types/account-types.js';
 import type {
   IdentityKeysBlob,
   SignedIdentityKeysBlob,
 } from 'lib/types/crypto-types.js';
 import type { CalendarQuery } from 'lib/types/entry-types.js';
 import { defaultNumberPerThread } from 'lib/types/message-types.js';
 import type {
   SIWEAuthRequest,
   SIWEMessage,
   SIWESocialProof,
 } from 'lib/types/siwe-types.js';
 import type {
   SubscriptionUpdateRequest,
   SubscriptionUpdateResponse,
 } from 'lib/types/subscription-types.js';
 import type { PasswordUpdate } from 'lib/types/user-types.js';
+import {
+  identityKeysBlobValidator,
+  signedIdentityKeysBlobValidator,
+} from 'lib/utils/crypto-utils.js';
 import { ServerError } from 'lib/utils/errors.js';
 import { values } from 'lib/utils/objects.js';
 import { promiseAll } from 'lib/utils/promises.js';
 import {
   getPublicKeyFromSIWEStatement,
   isValidSIWEMessage,
   isValidSIWEStatementWithPublicKey,
   primaryIdentityPublicKeyRegex,
 } from 'lib/utils/siwe-utils.js';
 import {
   tShape,
   tPlatformDetails,
   tPassword,
   tEmail,
   tOldValidUsername,
   tRegex,
 } from 'lib/utils/validation-utils.js';
 
 import {
   entryQueryInputValidator,
   newEntryQueryInputValidator,
   normalizeCalendarQuery,
   verifyCalendarQueryThreadIDs,
 } from './entry-responders.js';
 import { handleAsyncPromise } from './handlers.js';
 import {
   createAccount,
   processSIWEAccountCreation,
 } from '../creators/account-creator.js';
 import { dbQuery, SQL } from '../database/database.js';
 import { deleteAccount } from '../deleters/account-deleters.js';
 import { deleteCookie } from '../deleters/cookie-deleters.js';
 import { checkAndInvalidateSIWENonceEntry } from '../deleters/siwe-nonce-deleters.js';
 import { fetchEntryInfos } from '../fetchers/entry-fetchers.js';
 import { fetchMessageInfos } from '../fetchers/message-fetchers.js';
 import { fetchNotAcknowledgedPolicies } from '../fetchers/policy-acknowledgment-fetchers.js';
 import { fetchThreadInfos } from '../fetchers/thread-fetchers.js';
 import {
   fetchKnownUserInfos,
   fetchLoggedInUserInfo,
   fetchUserIDForEthereumAddress,
 } from '../fetchers/user-fetchers.js';
 import {
   createNewAnonymousCookie,
   createNewUserCookie,
   setNewSession,
 } from '../session/cookies.js';
 import type { Viewer } from '../session/viewer.js';
 import {
   accountUpdater,
   checkAndSendVerificationEmail,
   checkAndSendPasswordResetEmail,
   updatePassword,
   updateUserSettings,
 } from '../updaters/account-updaters.js';
 import { userSubscriptionUpdater } from '../updaters/user-subscription-updaters.js';
 import { viewerAcknowledgmentUpdater } from '../updaters/viewer-acknowledgment-updater.js';
 import { getOLMUtility } from '../utils/olm-utils.js';
 import type { OLMUtility } from '../utils/olm-utils.js';
 import { validateInput } from '../utils/validation-utils.js';
 
 const subscriptionUpdateRequestInputValidator = tShape({
   threadID: t.String,
   updatedFields: tShape({
     pushNotifs: t.maybe(t.Boolean),
     home: t.maybe(t.Boolean),
   }),
 });
 
 async function userSubscriptionUpdateResponder(
   viewer: Viewer,
   input: any,
 ): Promise<SubscriptionUpdateResponse> {
   const request: SubscriptionUpdateRequest = input;
   await validateInput(viewer, subscriptionUpdateRequestInputValidator, request);
   const threadSubscription = await userSubscriptionUpdater(viewer, request);
   return { threadSubscription };
 }
 
 const accountUpdateInputValidator = tShape({
   updatedFields: tShape({
     email: t.maybe(tEmail),
     password: t.maybe(tPassword),
   }),
   currentPassword: tPassword,
 });
 
 async function passwordUpdateResponder(
   viewer: Viewer,
   input: any,
 ): Promise<void> {
   const request: PasswordUpdate = input;
   await validateInput(viewer, accountUpdateInputValidator, request);
   await accountUpdater(viewer, request);
 }
 
 async function sendVerificationEmailResponder(viewer: Viewer): Promise<void> {
   await validateInput(viewer, null, null);
   await checkAndSendVerificationEmail(viewer);
 }
 
 const resetPasswordRequestInputValidator = tShape({
   usernameOrEmail: t.union([tEmail, tOldValidUsername]),
 });
 
 async function sendPasswordResetEmailResponder(
   viewer: Viewer,
   input: any,
 ): Promise<void> {
   const request: ResetPasswordRequest = input;
   await validateInput(viewer, resetPasswordRequestInputValidator, request);
   await checkAndSendPasswordResetEmail(request);
 }
 
 async function logOutResponder(viewer: Viewer): Promise<LogOutResponse> {
   await validateInput(viewer, null, null);
   if (viewer.loggedIn) {
     const [anonymousViewerData] = await Promise.all([
       createNewAnonymousCookie({
         platformDetails: viewer.platformDetails,
         deviceToken: viewer.deviceToken,
       }),
       deleteCookie(viewer.cookieID),
     ]);
     viewer.setNewCookie(anonymousViewerData);
   }
   return {
     currentUserInfo: {
       id: viewer.id,
       anonymous: true,
     },
   };
 }
 
 const deleteAccountRequestInputValidator = tShape({
   password: t.maybe(tPassword),
 });
 
 async function accountDeletionResponder(
   viewer: Viewer,
   input: any,
 ): Promise<LogOutResponse> {
   const request: DeleteAccountRequest = input;
   await validateInput(viewer, deleteAccountRequestInputValidator, request);
   const result = await deleteAccount(viewer, request);
   invariant(result, 'deleteAccount should return result if handed request');
   return result;
 }
 
 const deviceTokenUpdateRequestInputValidator = tShape({
   deviceType: t.maybe(t.enums.of(['ios', 'android'])),
   deviceToken: t.String,
 });
 
-const signedIdentityKeysBlobValidator = tShape({
-  payload: t.String,
-  signature: t.String,
-});
-
 const registerRequestInputValidator = tShape({
   username: t.String,
   email: t.maybe(tEmail),
   password: tPassword,
   calendarQuery: t.maybe(newEntryQueryInputValidator),
   deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
   platformDetails: tPlatformDetails,
   // We include `primaryIdentityPublicKey` to avoid breaking
   // old clients, but we no longer do anything with it.
   primaryIdentityPublicKey: t.maybe(tRegex(primaryIdentityPublicKeyRegex)),
   signedIdentityKeysBlob: t.maybe(signedIdentityKeysBlobValidator),
 });
 
 async function accountCreationResponder(
   viewer: Viewer,
   input: any,
 ): Promise<RegisterResponse> {
   const request: RegisterRequest = input;
   await validateInput(viewer, registerRequestInputValidator, request);
   const { signedIdentityKeysBlob } = request;
   if (signedIdentityKeysBlob) {
     const identityKeys: IdentityKeysBlob = JSON.parse(
       signedIdentityKeysBlob.payload,
     );
+    if (!identityKeysBlobValidator.is(identityKeys)) {
+      throw new ServerError('invalid_identity_keys_blob');
+    }
 
     const olmUtil: OLMUtility = getOLMUtility();
     try {
       olmUtil.ed25519_verify(
         identityKeys.primaryIdentityPublicKeys.ed25519,
         signedIdentityKeysBlob.payload,
         signedIdentityKeysBlob.signature,
       );
     } catch (e) {
       throw new ServerError('invalid_signature');
     }
   }
   return await createAccount(viewer, request);
 }
 
 type ProcessSuccessfulLoginParams = {
   +viewer: Viewer,
   +input: any,
   +userID: string,
   +calendarQuery: ?CalendarQuery,
   +socialProof?: ?SIWESocialProof,
   +signedIdentityKeysBlob?: ?SignedIdentityKeysBlob,
 };
 
 async function processSuccessfulLogin(
   params: ProcessSuccessfulLoginParams,
 ): Promise<LogInResponse> {
   const {
     viewer,
     input,
     userID,
     calendarQuery,
     socialProof,
     signedIdentityKeysBlob,
   } = params;
 
   const request: LogInRequest = input;
   const newServerTime = Date.now();
   const deviceToken = request.deviceTokenUpdateRequest
     ? request.deviceTokenUpdateRequest.deviceToken
     : viewer.deviceToken;
   const [userViewerData, notAcknowledgedPolicies] = await Promise.all([
     createNewUserCookie(userID, {
       platformDetails: request.platformDetails,
       deviceToken,
       socialProof,
       signedIdentityKeysBlob,
     }),
     fetchNotAcknowledgedPolicies(userID, baseLegalPolicies),
     deleteCookie(viewer.cookieID),
   ]);
   viewer.setNewCookie(userViewerData);
 
   if (
     notAcknowledgedPolicies.length &&
     hasMinCodeVersion(viewer.platformDetails, 181)
   ) {
     const currentUserInfo = await fetchLoggedInUserInfo(viewer);
     return {
       notAcknowledgedPolicies,
       currentUserInfo: currentUserInfo,
       rawMessageInfos: [],
       truncationStatuses: {},
       userInfos: [],
       rawEntryInfos: [],
       serverTime: 0,
       cookieChange: {
         threadInfos: {},
         userInfos: [],
       },
     };
   }
 
   if (calendarQuery) {
     await setNewSession(viewer, calendarQuery, newServerTime);
   }
 
   const threadCursors = {};
   for (const watchedThreadID of request.watchedIDs) {
     threadCursors[watchedThreadID] = null;
   }
   const messageSelectionCriteria = { threadCursors, joinedThreads: true };
 
   const [
     threadsResult,
     messagesResult,
     entriesResult,
     userInfos,
     currentUserInfo,
   ] = await Promise.all([
     fetchThreadInfos(viewer),
     fetchMessageInfos(viewer, messageSelectionCriteria, defaultNumberPerThread),
     calendarQuery ? fetchEntryInfos(viewer, [calendarQuery]) : undefined,
     fetchKnownUserInfos(viewer),
     fetchLoggedInUserInfo(viewer),
   ]);
 
   const rawEntryInfos = entriesResult ? entriesResult.rawEntryInfos : null;
   const response: LogInResponse = {
     currentUserInfo,
     rawMessageInfos: messagesResult.rawMessageInfos,
     truncationStatuses: messagesResult.truncationStatuses,
     serverTime: newServerTime,
     userInfos: values(userInfos),
     cookieChange: {
       threadInfos: threadsResult.threadInfos,
       userInfos: [],
     },
   };
   if (rawEntryInfos) {
     return {
       ...response,
       rawEntryInfos,
     };
   }
   return response;
 }
 
 const logInRequestInputValidator = tShape({
   username: t.maybe(t.String),
   usernameOrEmail: t.maybe(t.union([tEmail, tOldValidUsername])),
   password: tPassword,
   watchedIDs: t.list(t.String),
   calendarQuery: t.maybe(entryQueryInputValidator),
   deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
   platformDetails: tPlatformDetails,
   source: t.maybe(t.enums.of(values(logInActionSources))),
   // We include `primaryIdentityPublicKey` to avoid breaking
   // old clients, but we no longer do anything with it.
   primaryIdentityPublicKey: t.maybe(tRegex(primaryIdentityPublicKeyRegex)),
   signedIdentityKeysBlob: t.maybe(signedIdentityKeysBlobValidator),
 });
 
 async function logInResponder(
   viewer: Viewer,
   input: any,
 ): Promise<LogInResponse> {
   await validateInput(viewer, logInRequestInputValidator, input);
   const request: LogInRequest = input;
 
   let identityKeys: ?IdentityKeysBlob;
   const { signedIdentityKeysBlob } = request;
   if (signedIdentityKeysBlob) {
     identityKeys = JSON.parse(signedIdentityKeysBlob.payload);
 
     const olmUtil: OLMUtility = getOLMUtility();
     try {
       olmUtil.ed25519_verify(
         identityKeys.primaryIdentityPublicKeys.ed25519,
         signedIdentityKeysBlob.payload,
         signedIdentityKeysBlob.signature,
       );
     } catch (e) {
       throw new ServerError('invalid_signature');
     }
   }
 
   const calendarQuery = request.calendarQuery
     ? normalizeCalendarQuery(request.calendarQuery)
     : null;
   const promises = {};
   if (calendarQuery) {
     promises.verifyCalendarQueryThreadIDs =
       verifyCalendarQueryThreadIDs(calendarQuery);
   }
   const username = request.username ?? request.usernameOrEmail;
   if (!username) {
     if (hasMinCodeVersion(viewer.platformDetails, 150)) {
       throw new ServerError('invalid_credentials');
     } else {
       throw new ServerError('invalid_parameters');
     }
   }
   const userQuery = SQL`
     SELECT id, hash, username
     FROM users
     WHERE LCASE(username) = LCASE(${username})
   `;
   promises.userQuery = dbQuery(userQuery);
   promises.rustAPI = getRustAPI();
   const {
     userQuery: [userResult],
     rustAPI,
   } = await promiseAll(promises);
 
   if (userResult.length === 0) {
     if (hasMinCodeVersion(viewer.platformDetails, 150)) {
       throw new ServerError('invalid_credentials');
     } else {
       throw new ServerError('invalid_parameters');
     }
   }
 
   const userRow = userResult[0];
 
   if (!userRow.hash || !bcrypt.compareSync(request.password, userRow.hash)) {
     throw new ServerError('invalid_credentials');
   }
 
   const id = userRow.id.toString();
 
   if (identityKeys && signedIdentityKeysBlob) {
     handleAsyncPromise(
       rustAPI.loginUserPake(
         id,
         identityKeys.primaryIdentityPublicKeys.ed25519,
         request.password,
         signedIdentityKeysBlob,
       ),
     );
   }
 
   return await processSuccessfulLogin({
     viewer,
     input,
     userID: id,
     calendarQuery,
     signedIdentityKeysBlob,
   });
 }
 
 const siweAuthRequestInputValidator = tShape({
   signature: t.String,
   message: t.String,
   calendarQuery: entryQueryInputValidator,
   deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
   platformDetails: tPlatformDetails,
   watchedIDs: t.list(t.String),
   signedIdentityKeysBlob: t.maybe(signedIdentityKeysBlobValidator),
 });
 
 async function siweAuthResponder(
   viewer: Viewer,
   input: any,
 ): Promise<LogInResponse> {
   await validateInput(viewer, siweAuthRequestInputValidator, input);
   const request: SIWEAuthRequest = input;
   const {
     message,
     signature,
     deviceTokenUpdateRequest,
     platformDetails,
     signedIdentityKeysBlob,
   } = request;
   const calendarQuery = normalizeCalendarQuery(request.calendarQuery);
 
   // 1. Ensure that `message` is a well formed Comm SIWE Auth message.
   const siweMessage: SIWEMessage = new SiweMessage(message);
   if (!isValidSIWEMessage(siweMessage)) {
     throw new ServerError('invalid_parameters');
   }
 
   // 2. Ensure that the `nonce` exists in the `siwe_nonces` table
   //    AND hasn't expired. If those conditions are met, delete the entry to
   //    ensure that the same `nonce` can't be re-used in a future request.
   const wasNonceCheckedAndInvalidated = await checkAndInvalidateSIWENonceEntry(
     siweMessage.nonce,
   );
   if (!wasNonceCheckedAndInvalidated) {
     throw new ServerError('invalid_parameters');
   }
 
   // 3. Validate SIWEMessage signature and handle possible errors.
   try {
     await siweMessage.validate(signature);
   } catch (error) {
     if (error === ErrorTypes.EXPIRED_MESSAGE) {
       // Thrown when the `expirationTime` is present and in the past.
       throw new ServerError('expired_message');
     } else if (error === ErrorTypes.INVALID_SIGNATURE) {
       // Thrown when the `validate()` function can't verify the message.
       throw new ServerError('invalid_signature');
     } else if (error === ErrorTypes.MALFORMED_SESSION) {
       // Thrown when some required field is missing.
       throw new ServerError('malformed_session');
     } else {
       throw new ServerError('unknown_error');
     }
   }
 
   // 4. Pull `primaryIdentityPublicKey` out from SIWEMessage `statement`.
   //    We expect it to be included for BOTH native and web clients.
   const { statement } = siweMessage;
   const primaryIdentityPublicKey =
     statement && isValidSIWEStatementWithPublicKey(statement)
       ? getPublicKeyFromSIWEStatement(statement)
       : null;
   if (!primaryIdentityPublicKey) {
     throw new ServerError('invalid_siwe_statement_public_key');
   }
 
   // 5. Verify `signedIdentityKeysBlob.payload` with included `signature`
   //    if `signedIdentityKeysBlob` was included in the `SIWEAuthRequest`.
   let identityKeys: ?IdentityKeysBlob;
   if (signedIdentityKeysBlob) {
     identityKeys = JSON.parse(signedIdentityKeysBlob.payload);
+    if (!identityKeysBlobValidator.is(identityKeys)) {
+      throw new ServerError('invalid_identity_keys_blob');
+    }
+
     const olmUtil: OLMUtility = getOLMUtility();
     try {
       olmUtil.ed25519_verify(
         identityKeys.primaryIdentityPublicKeys.ed25519,
         signedIdentityKeysBlob.payload,
         signedIdentityKeysBlob.signature,
       );
     } catch (e) {
       throw new ServerError('invalid_signature');
     }
   }
 
   // 6. Ensure that `primaryIdentityPublicKeys.ed25519` matches SIWE
   //    statement `primaryIdentityPublicKey` if `identityKeys` exists.
   if (
     identityKeys &&
     identityKeys.primaryIdentityPublicKeys.ed25519 !== primaryIdentityPublicKey
   ) {
     throw new ServerError('primary_public_key_mismatch');
   }
 
   // 7. Construct `SIWESocialProof` object with the stringified
   //    SIWEMessage and the corresponding signature.
   const socialProof: SIWESocialProof = {
     siweMessage: siweMessage.toMessage(),
     siweMessageSignature: signature,
   };
 
   // 8. Create account with call to `processSIWEAccountCreation(...)`
   //    if address does not correspond to an existing user.
   let userID = await fetchUserIDForEthereumAddress(siweMessage.address);
   if (!userID) {
     const siweAccountCreationRequest = {
       address: siweMessage.address,
       calendarQuery,
       deviceTokenUpdateRequest,
       platformDetails,
       socialProof,
     };
     userID = await processSIWEAccountCreation(
       viewer,
       siweAccountCreationRequest,
     );
   }
 
   // 9. Try to double-write SIWE account info to the Identity service
   const userIDCopy = userID;
   if (identityKeys && signedIdentityKeysBlob) {
     const identityKeysCopy = identityKeys;
     handleAsyncPromise(
       (async () => {
         const rustAPI = await getRustAPI();
         rustAPI.loginUserWallet(
           userIDCopy,
           identityKeysCopy.primaryIdentityPublicKeys.ed25519,
           siweMessage.toMessage(),
           signature,
           signedIdentityKeysBlob,
           JSON.stringify(socialProof),
         );
       })(),
     );
   }
 
   // 10. Complete login with call to `processSuccessfulLogin(...)`.
   return await processSuccessfulLogin({
     viewer,
     input,
     userID,
     calendarQuery,
     socialProof,
     signedIdentityKeysBlob,
   });
 }
 
 const updatePasswordRequestInputValidator = tShape({
   code: t.String,
   password: tPassword,
   watchedIDs: t.list(t.String),
   calendarQuery: t.maybe(entryQueryInputValidator),
   deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
   platformDetails: tPlatformDetails,
 });
 
 async function oldPasswordUpdateResponder(
   viewer: Viewer,
   input: any,
 ): Promise<LogInResponse> {
   await validateInput(viewer, updatePasswordRequestInputValidator, input);
   const request: UpdatePasswordRequest = input;
   if (request.calendarQuery) {
     request.calendarQuery = normalizeCalendarQuery(request.calendarQuery);
   }
   return await updatePassword(viewer, request);
 }
 
 const updateUserSettingsInputValidator = tShape({
   name: t.irreducible(
     userSettingsTypes.DEFAULT_NOTIFICATIONS,
     x => x === userSettingsTypes.DEFAULT_NOTIFICATIONS,
   ),
   data: t.enums.of(notificationTypeValues),
 });
 
 async function updateUserSettingsResponder(
   viewer: Viewer,
   input: any,
 ): Promise<void> {
   const request: UpdateUserSettingsRequest = input;
   await validateInput(viewer, updateUserSettingsInputValidator, request);
   return await updateUserSettings(viewer, request);
 }
 
 const policyAcknowledgmentRequestInputValidator = tShape({
   policy: t.maybe(t.enums.of(policies)),
 });
 
 async function policyAcknowledgmentResponder(
   viewer: Viewer,
   input: any,
 ): Promise<void> {
   const request: PolicyAcknowledgmentRequest = input;
   await validateInput(
     viewer,
     policyAcknowledgmentRequestInputValidator,
     request,
   );
   await viewerAcknowledgmentUpdater(viewer, request.policy);
 }
 
 export {
   userSubscriptionUpdateResponder,
   passwordUpdateResponder,
   sendVerificationEmailResponder,
   sendPasswordResetEmailResponder,
   logOutResponder,
   accountDeletionResponder,
   accountCreationResponder,
   logInResponder,
   siweAuthResponder,
   oldPasswordUpdateResponder,
   updateUserSettingsResponder,
   policyAcknowledgmentResponder,
 };
diff --git a/lib/utils/crypto-utils.js b/lib/utils/crypto-utils.js
index 747f4c983..78bfae7db 100644
--- a/lib/utils/crypto-utils.js
+++ b/lib/utils/crypto-utils.js
@@ -1,5 +1,30 @@
 // @flow
 
+import t from 'tcomb';
+import { type TInterface } from 'tcomb';
+
+import { primaryIdentityPublicKeyRegex } from './siwe-utils.js';
+import { tRegex, tShape } from './validation-utils.js';
+
 const minimumOneTimeKeysRequired = 10;
 
-export { minimumOneTimeKeysRequired };
+const signedIdentityKeysBlobValidator: TInterface = tShape({
+  payload: t.String,
+  signature: t.String,
+});
+
+const olmIdentityKeysValidator: TInterface = tShape({
+  ed25519: tRegex(primaryIdentityPublicKeyRegex),
+  curve25519: tRegex(primaryIdentityPublicKeyRegex),
+});
+
+const identityKeysBlobValidator: TInterface = tShape({
+  primaryIdentityPublicKeys: olmIdentityKeysValidator,
+  notificationIdentityPublicKeys: olmIdentityKeysValidator,
+});
+
+export {
+  minimumOneTimeKeysRequired,
+  signedIdentityKeysBlobValidator,
+  identityKeysBlobValidator,
+};