diff --git a/keyserver/src/responders/landing-handler.js b/keyserver/src/responders/landing-handler.js
--- a/keyserver/src/responders/landing-handler.js
+++ b/keyserver/src/responders/landing-handler.js
@@ -11,6 +11,7 @@
 import {
   isValidPrimaryIdentityPublicKey,
   isValidSIWENonce,
+  isValidSIWEMessageType,
 } from 'lib/utils/siwe-utils.js';
 
 import { getMessageForException } from './utils.js';
@@ -138,6 +139,17 @@
     });
     return;
   }
+  const siweMessageType = req.header('siwe-message-type');
+  if (
+    siweMessageType !== null &&
+    siweMessageType !== undefined &&
+    !isValidSIWEMessageType(siweMessageType)
+  ) {
+    res.status(400).send({
+      message: 'Invalid siwe message type.',
+    });
+    return;
+  }
 
   const [{ jsURL, fontURLs, cssInclude }, LandingSSR] = await Promise.all([
     getAssetInfo(),
@@ -200,6 +212,7 @@
       basename={routerBasename}
       siweNonce={siweNonce}
       siwePrimaryIdentityPublicKey={siwePrimaryIdentityPublicKey}
+      siweMessageType={siweMessageType}
     />,
   );
   reactStream.pipe(res, { end: false });
@@ -209,11 +222,15 @@
   const siwePrimaryIdentityPublicKeyString = siwePrimaryIdentityPublicKey
     ? `"${siwePrimaryIdentityPublicKey}"`
     : 'null';
+  const siweMessageTypeString = siweMessageType
+    ? `"${siweMessageType}"`
+    : 'null';
   // prettier-ignore
   res.end(html`</div>
         <script>var routerBasename = "${routerBasename}";</script>
         <script>var siweNonce = ${siweNonceString};</script>
         <script>var siwePrimaryIdentityPublicKey = ${siwePrimaryIdentityPublicKeyString};</script>
+        <script>var siweMessageType = ${siweMessageTypeString};</script>
         <script src="${jsURL}"></script>
       </body>
     </html>
diff --git a/landing/landing-ssr.react.js b/landing/landing-ssr.react.js
--- a/landing/landing-ssr.react.js
+++ b/landing/landing-ssr.react.js
@@ -11,16 +11,24 @@
   +basename: string,
   +siweNonce: ?string,
   +siwePrimaryIdentityPublicKey: ?string,
+  +siweMessageType: ?string,
 };
 function LandingSSR(props: LandingSSRProps): React.Node {
-  const { url, basename, siweNonce, siwePrimaryIdentityPublicKey } = props;
+  const {
+    url,
+    basename,
+    siweNonce,
+    siwePrimaryIdentityPublicKey,
+    siweMessageType,
+  } = props;
 
   const siweContextValue = React.useMemo(
     () => ({
       siweNonce,
       siwePrimaryIdentityPublicKey,
+      siweMessageType,
     }),
-    [siweNonce, siwePrimaryIdentityPublicKey],
+    [siweNonce, siwePrimaryIdentityPublicKey, siweMessageType],
   );
   const routerContext = React.useMemo(() => ({}), []);
   return (
diff --git a/landing/root.js b/landing/root.js
--- a/landing/root.js
+++ b/landing/root.js
@@ -9,12 +9,14 @@
 declare var routerBasename: string;
 declare var siweNonce: ?string;
 declare var siwePrimaryIdentityPublicKey: ?string;
+declare var siweMessageType: ?string;
 
 function RootComponent(): React.Node {
   const siweContextValue = React.useMemo(
     () => ({
       siweNonce,
       siwePrimaryIdentityPublicKey,
+      siweMessageType,
     }),
     [],
   );
diff --git a/landing/siwe-context.js b/landing/siwe-context.js
--- a/landing/siwe-context.js
+++ b/landing/siwe-context.js
@@ -5,11 +5,13 @@
 export type SIWEContextType = {
   +siweNonce: ?string,
   +siwePrimaryIdentityPublicKey: ?string,
+  +siweMessageType: ?string,
 };
 
 const SIWEContext: React.Context<SIWEContextType> = React.createContext({
   siweNonce: null,
   siwePrimaryIdentityPublicKey: null,
+  siweMessageType: null,
 });
 
 export { SIWEContext };
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
@@ -136,3 +136,15 @@
   +signature: string,
   +fid?: ?string,
 };
+
+export const SIWEMessageTypes = Object.freeze({
+  MSG_AUTH: 'msg_auth',
+  MSG_BACKUP: 'msg_backup',
+});
+
+export type SIWEMessageType = $Values<typeof SIWEMessageTypes>;
+
+export type SIWEBackupSecrets = {
+  +message: string,
+  +signature: string,
+};
diff --git a/lib/utils/siwe-utils.js b/lib/utils/siwe-utils.js
--- a/lib/utils/siwe-utils.js
+++ b/lib/utils/siwe-utils.js
@@ -2,9 +2,11 @@
 
 import invariant from 'invariant';
 import { SiweMessage } from 'siwe';
+import t, { type TEnums } from 'tcomb';
 
 import { isDev } from './dev-utils.js';
-import type { SIWEMessage } from '../types/siwe-types.js';
+import { type SIWEMessage, SIWEMessageTypes } from '../types/siwe-types.js';
+import { values } from '../utils/objects.js';
 
 const siweNonceRegex: RegExp = /^[a-zA-Z0-9]{17}$/;
 function isValidSIWENonce(candidate: string): boolean {
@@ -21,6 +23,11 @@
   return primaryIdentityPublicKeyRegex.test(candidate);
 }
 
+const siweMessageTypeValidator: TEnums = t.enums.of(values(SIWEMessageTypes));
+function isValidSIWEMessageType(candidate: string): boolean {
+  return siweMessageTypeValidator.is(candidate);
+}
+
 const siweStatementLegalAgreement: string =
   'By continuing, I accept the Comm Terms of Service: https://comm.app/terms';
 
@@ -111,6 +118,7 @@
 export {
   isValidSIWENonce,
   isValidEthereumAddress,
+  isValidSIWEMessageType,
   primaryIdentityPublicKeyRegex,
   isValidPrimaryIdentityPublicKey,
   createSIWEMessage,
diff --git a/native/account/fullscreen-siwe-panel.react.js b/native/account/fullscreen-siwe-panel.react.js
--- a/native/account/fullscreen-siwe-panel.react.js
+++ b/native/account/fullscreen-siwe-panel.react.js
@@ -6,7 +6,7 @@
 import { ActivityIndicator, View } from 'react-native';
 
 import { setDataLoadedActionType } from 'lib/actions/client-db-store-actions.js';
-import type { SIWEResult } from 'lib/types/siwe-types.js';
+import { type SIWEResult, SIWEMessageTypes } from 'lib/types/siwe-types.js';
 import { ServerError } from 'lib/utils/errors.js';
 import { useDispatch } from 'lib/utils/redux-utils.js';
 import { usingCommServicesAccessToken } from 'lib/utils/services-utils.js';
@@ -152,6 +152,7 @@
         onClosed={ifBeforeSuccessGoBackToPrompt}
         onClosing={ifBeforeSuccessGoBackToPrompt}
         onSuccessfulWalletSignature={onSuccess}
+        siweMessageType={SIWEMessageTypes.MSG_AUTH}
         setLoading={setLoading}
       />
     </>
diff --git a/native/account/registration/connect-ethereum.react.js b/native/account/registration/connect-ethereum.react.js
--- a/native/account/registration/connect-ethereum.react.js
+++ b/native/account/registration/connect-ethereum.react.js
@@ -9,7 +9,7 @@
   exactSearchUserActionTypes,
 } from 'lib/actions/user-actions.js';
 import { createLoadingStatusSelector } from 'lib/selectors/loading-selectors.js';
-import type { SIWEResult } from 'lib/types/siwe-types.js';
+import { type SIWEResult, SIWEMessageTypes } from 'lib/types/siwe-types.js';
 import { useLegacyAshoatKeyserverCall } from 'lib/utils/action-utils.js';
 import { useDispatchActionPromise } from 'lib/utils/redux-promise-utils.js';
 import { usingCommServicesAccessToken } from 'lib/utils/services-utils.js';
@@ -200,6 +200,7 @@
         onClosed={onPanelClosed}
         closing={panelState === 'closing'}
         onSuccessfulWalletSignature={onSuccessfulWalletSignature}
+        siweMessageType={SIWEMessageTypes.MSG_AUTH}
         setLoading={siwePanelSetLoading}
         keyserverCallParamOverride={serverCallParamOverride}
       />
diff --git a/native/account/siwe-panel.react.js b/native/account/siwe-panel.react.js
--- a/native/account/siwe-panel.react.js
+++ b/native/account/siwe-panel.react.js
@@ -16,7 +16,11 @@
 } from 'lib/actions/user-actions.js';
 import type { ServerCallSelectorParams } from 'lib/keyserver-conn/call-keyserver-endpoint-provider.react.js';
 import { createLoadingStatusSelector } from 'lib/selectors/loading-selectors.js';
-import type { SIWEWebViewMessage, SIWEResult } from 'lib/types/siwe-types.js';
+import type {
+  SIWEWebViewMessage,
+  SIWEResult,
+  SIWEMessageType,
+} from 'lib/types/siwe-types.js';
 import { useLegacyAshoatKeyserverCall } from 'lib/utils/action-utils.js';
 import { getContentSigningKey } from 'lib/utils/crypto-utils.js';
 import { useDispatchActionPromise } from 'lib/utils/redux-promise-utils.js';
@@ -45,6 +49,7 @@
   +onClosed: () => mixed,
   +onClosing: () => mixed,
   +onSuccessfulWalletSignature: SIWEResult => mixed,
+  +siweMessageType: SIWEMessageType,
   +closing: boolean,
   +setLoading: boolean => mixed,
   +keyserverCallParamOverride?: Partial<ServerCallSelectorParams>,
@@ -65,6 +70,7 @@
   );
 
   const { onClosing } = props;
+  const { siweMessageType } = props;
 
   const legacySiweAuthCallLoading = useSelector(
     state => legacySiweAuthLoadingStatusSelector(state) === 'loading',
@@ -186,9 +192,10 @@
       headers: {
         'siwe-nonce': nonce,
         'siwe-primary-identity-public-key': primaryIdentityPublicKey,
+        'siwe-message-type': siweMessageType,
       },
     }),
-    [nonce, primaryIdentityPublicKey],
+    [nonce, primaryIdentityPublicKey, siweMessageType],
   );
 
   const onWebViewLoaded = React.useCallback(() => {