diff --git a/package.json b/package.json
index 9196a3dc8..2c72d2e11 100644
--- a/package.json
+++ b/package.json
@@ -198,7 +198,7 @@
     "@electron/fuses": "1.5.0",
     "@formatjs/intl": "2.6.7",
     "@mixer/parallel-prettier": "2.0.3",
-    "@signalapp/mock-server": "4.2.0",
+    "@signalapp/mock-server": "4.3.0",
     "@storybook/addon-a11y": "7.4.5",
     "@storybook/addon-actions": "7.4.5",
     "@storybook/addon-controls": "7.4.5",
diff --git a/protos/DeviceMessages.proto b/protos/DeviceMessages.proto
index 30174af3a..3809a47a2 100644
--- a/protos/DeviceMessages.proto
+++ b/protos/DeviceMessages.proto
@@ -26,6 +26,7 @@ message ProvisionMessage {
   optional bytes   profileKey = 6;
   optional bool    readReceipts = 7;
   optional uint32  ProvisioningVersion = 9;
+  optional bytes   masterKey = 13;
 }
 
 enum ProvisioningVersion {
diff --git a/ts/textsecure/AccountManager.ts b/ts/textsecure/AccountManager.ts
index 9d2541de9..8f3db2a4f 100644
--- a/ts/textsecure/AccountManager.ts
+++ b/ts/textsecure/AccountManager.ts
@@ -67,6 +67,7 @@ const DAY = 24 * 60 * 60 * 1000;
 
 const STARTING_KEY_ID = 1;
 const PROFILE_KEY_LENGTH = 32;
+const MASTER_KEY_LENGTH = 32;
 const KEY_TOO_OLD_THRESHOLD = 14 * DAY;
 
 export const KYBER_KEY_ID_KEY: StorageKeyByServiceIdKind = {
@@ -120,6 +121,7 @@ type CreateAccountSharedOptionsType = Readonly<{
   aciKeyPair: KeyPairType;
   pniKeyPair: KeyPairType;
   profileKey: Uint8Array;
+  masterKey: Uint8Array | undefined;
 }>;
 
 type CreatePrimaryDeviceOptionsType = Readonly<{
@@ -302,6 +304,7 @@ export default class AccountManager extends EventTarget {
       const pniKeyPair = generateKeyPair();
       const profileKey = getRandomBytes(PROFILE_KEY_LENGTH);
       const accessKey = deriveAccessKey(profileKey);
+      const masterKey = getRandomBytes(MASTER_KEY_LENGTH);
 
       const registrationBaton = this.server.startRegistration();
       try {
@@ -314,6 +317,7 @@ export default class AccountManager extends EventTarget {
           pniKeyPair,
           profileKey,
           accessKey,
+          masterKey,
           readReceipts: true,
         });
       } finally {
@@ -428,6 +432,7 @@ export default class AccountManager extends EventTarget {
           ourAci,
           ourPni,
           readReceipts: Boolean(provisionMessage.readReceipts),
+          masterKey: provisionMessage.masterKey,
         });
       } finally {
         this.server.finishRegistration(registrationBaton);
@@ -968,6 +973,7 @@ export default class AccountManager extends EventTarget {
       aciKeyPair,
       pniKeyPair,
       profileKey,
+      masterKey,
       readReceipts,
       userAgent,
     } = options;
@@ -1202,6 +1208,9 @@ export default class AccountManager extends EventTarget {
     if (userAgent) {
       await storage.put('userAgent', userAgent);
     }
+    if (masterKey) {
+      await storage.put('masterKey', Bytes.toBase64(masterKey));
+    }
 
     await storage.put('read-receipt-setting', Boolean(readReceipts));
 
diff --git a/ts/textsecure/ProvisioningCipher.ts b/ts/textsecure/ProvisioningCipher.ts
index 78f5d29d8..0b31b6519 100644
--- a/ts/textsecure/ProvisioningCipher.ts
+++ b/ts/textsecure/ProvisioningCipher.ts
@@ -24,6 +24,7 @@ type ProvisionDecryptResult = {
   userAgent?: string;
   readReceipts?: boolean;
   profileKey?: Uint8Array;
+  masterKey?: Uint8Array;
 };
 
 class ProvisioningCipherInner {
@@ -87,6 +88,9 @@ class ProvisioningCipherInner {
     if (provisionMessage.profileKey) {
       ret.profileKey = provisionMessage.profileKey;
     }
+    if (provisionMessage.masterKey) {
+      ret.masterKey = provisionMessage.masterKey;
+    }
     return ret;
   }
 
diff --git a/yarn.lock b/yarn.lock
index 4e36103ea..09a8f9c3e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3901,10 +3901,10 @@
     node-gyp-build "^4.2.3"
     uuid "^8.3.0"
 
-"@signalapp/mock-server@4.2.0":
-  version "4.2.0"
-  resolved "https://registry.yarnpkg.com/@signalapp/mock-server/-/mock-server-4.2.0.tgz#836bf1d8cb38b9f66a6f719205e5000cdc7d184b"
-  integrity sha512-pungaAf3Pel34yIK00nRtHWQHA9VCRjOH11ZBgrEjiMpdA+LPETCU94Do28Q9Un7T8GmNOJ0+cKAhCKuyo1Fow==
+"@signalapp/mock-server@4.3.0":
+  version "4.3.0"
+  resolved "https://registry.yarnpkg.com/@signalapp/mock-server/-/mock-server-4.3.0.tgz#501d1e0bc9f9fe811189690e7b053dfe9bac7c88"
+  integrity sha512-zE8+EhuKsQ0byXG1Prkw5hoH0pMySwf+AJNf2sdOTsIJSKLx8/GOP4uG3m/vSOW3m4BoAmVnpNzJryRIjpfAbw==
   dependencies:
     "@signalapp/libsignal-client" "^0.30.2"
     debug "^4.3.2"