diff --git a/src/crypto/backup.ts b/src/crypto/backup.ts
index 505409af2..ae87ce706 100644
--- a/src/crypto/backup.ts
+++ b/src/crypto/backup.ts
@@ -78,7 +78,7 @@ interface BackupAlgorithmClass {
         key: string | Uint8Array | null,
     ): Promise<[Uint8Array, AuthData]>;
 
-    checkBackupVersion(info: BackupInfo): void;
+    checkBackupVersion(info: IKeyBackupInfo): void;
 }
 
 interface BackupAlgorithm {
@@ -112,9 +112,9 @@ export class BackupManager {
      *
      * Throws an error if a problem is detected.
      *
-     * @param {BackupInfo} info the key backup info
+     * @param {IKeyBackupInfo} info the key backup info
      */
-    public static checkBackupVersion(info: BackupInfo): void {
+    public static checkBackupVersion(info: IKeyBackupInfo): void {
         const Algorithm = algorithmsByName[info.algorithm];
         if (!Algorithm) {
             throw new Error("Unknown backup algorithm: " + info.algorithm);
@@ -273,7 +273,7 @@ export class BackupManager {
     /**
      * Check if the given backup info is trusted.
      *
-     * @param {object} backupInfo key backup info dict from /room_keys/version
+     * @param {IKeyBackupInfo} backupInfo key backup info dict from /room_keys/version
      * @return {object} {
      *     usable: [bool], // is the backup trusted, true iff there is a sig that is valid & from a trusted device
      *     sigs: [
@@ -619,7 +619,7 @@ export class Curve25519 implements BackupAlgorithm {
         }
     }
 
-    public static checkBackupVersion(info: BackupInfo): void {
+    public static checkBackupVersion(info: IKeyBackupInfo): void {
         if (!info.auth_data.public_key) {
             throw new Error("Invalid backup data returned");
         }
@@ -754,7 +754,7 @@ export class Aes256 implements BackupAlgorithm {
         return [outKey, authData];
     }
 
-    public static checkBackupVersion(info: BackupInfo): void {
+    public static checkBackupVersion(info: IKeyBackupInfo): void {
         if (!info.auth_data.iv || !info.auth_data.mac) {
             throw new Error("Invalid backup data returned");
         }
diff --git a/src/crypto/index.ts b/src/crypto/index.ts
index 12b05ffac..74f0df5a4 100644
--- a/src/crypto/index.ts
+++ b/src/crypto/index.ts
@@ -126,6 +126,7 @@ export interface IMegolmSessionData {
     session_id: string;
     session_key: string;
     algorithm: string;
+    untrusted?: boolean;
 }
 /* eslint-enable camelcase */
 
diff --git a/src/crypto/key_passphrase.ts b/src/crypto/key_passphrase.ts
index ca11e7d2f..89aefc803 100644
--- a/src/crypto/key_passphrase.ts
+++ b/src/crypto/key_passphrase.ts
@@ -15,18 +15,13 @@ limitations under the License.
 */
 
 import { randomString } from '../randomstring';
+import { IKeyBackupInfo } from "./keybackup";
 
 const DEFAULT_ITERATIONS = 500000;
 
 const DEFAULT_BITSIZE = 256;
 
-/* eslint-disable camelcase */
-interface IAuthData {
-    private_key_salt: string;
-    private_key_iterations: number;
-    private_key_bits?: number;
-}
-/* eslint-enable camelcase */
+type IAuthData = IKeyBackupInfo["auth_data"];
 
 interface IKey {
     key: Uint8Array;
diff --git a/src/crypto/keybackup.ts b/src/crypto/keybackup.ts
index 123f18f76..d2cb481fa 100644
--- a/src/crypto/keybackup.ts
+++ b/src/crypto/keybackup.ts
@@ -35,11 +35,13 @@ export interface IKeyBackupRoomSessions {
 export interface IKeyBackupInfo {
     algorithm: string;
     auth_data: {
-        public_key: string;
-        signatures: ISignatures;
-        private_key_salt: string;
-        private_key_iterations: number;
+        public_key?: string;
+        signatures?: ISignatures;
+        private_key_salt?: string;
+        private_key_iterations?: number;
         private_key_bits?: number;
+        iv?: string;
+        mac?: string;
     };
     count?: number;
     etag?: string;