diff --git a/src/client.ts b/src/client.ts
index 263a2dcde..59a6fd772 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -2434,10 +2434,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns the VerificationRequest that is in progress, if any
      */
     public findVerificationRequestDMInProgress(roomId: string): VerificationRequest | undefined {
-        if (!this.crypto) {
+        if (!this.cryptoBackend) {
             throw new Error("End-to-end encryption disabled");
         }
-        return this.crypto.findVerificationRequestDMInProgress(roomId);
+        return this.cryptoBackend.findVerificationRequestDMInProgress(roomId);
     }
 
     /**
@@ -2594,10 +2594,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * @returns the cross signing information for the user.
      */
     public getStoredCrossSigningForUser(userId: string): CrossSigningInfo | null {
-        if (!this.crypto) {
+        if (!this.cryptoBackend) {
             throw new Error("End-to-end encryption disabled");
         }
-        return this.crypto.getStoredCrossSigningForUser(userId);
+        return this.cryptoBackend.getStoredCrossSigningForUser(userId);
     }
 
     /**
diff --git a/src/common-crypto/CryptoBackend.ts b/src/common-crypto/CryptoBackend.ts
index 5af90248a..6049cb765 100644
--- a/src/common-crypto/CryptoBackend.ts
+++ b/src/common-crypto/CryptoBackend.ts
@@ -18,9 +18,10 @@ import type { IDeviceLists, IToDeviceEvent } from "../sync-accumulator";
 import { MatrixEvent } from "../models/event";
 import { Room } from "../models/room";
 import { CryptoApi } from "../crypto-api";
-import { UserTrustLevel } from "../crypto/CrossSigning";
+import { CrossSigningInfo, UserTrustLevel } from "../crypto/CrossSigning";
 import { IEncryptedEventInfo } from "../crypto/api";
 import { IEventDecryptionResult } from "../@types/crypto";
+import { VerificationRequest } from "../crypto/verification/request/VerificationRequest";
 
 /**
  * Common interface for the crypto implementations
@@ -77,6 +78,26 @@ export interface CryptoBackend extends SyncCryptoCallbacks, CryptoApi {
      * @param event - event to be checked
      */
     getEventEncryptionInfo(event: MatrixEvent): IEncryptedEventInfo;
+
+    /**
+     * Finds a DM verification request that is already in progress for the given room id
+     *
+     * @param roomId - the room to use for verification
+     *
+     * @returns the VerificationRequest that is in progress, if any
+     */
+    findVerificationRequestDMInProgress(roomId: string): VerificationRequest | undefined;
+
+    /**
+     * Get the cross signing information for a given user.
+     *
+     * The cross-signing API is currently UNSTABLE and may change without notice.
+     *
+     * @param userId - the user ID to get the cross-signing info for.
+     *
+     * @returns the cross signing information for the user.
+     */
+    getStoredCrossSigningForUser(userId: string): CrossSigningInfo | null;
 }
 
 /** The methods which crypto implementations should expose to the Sync api */
diff --git a/src/rust-crypto/rust-crypto.ts b/src/rust-crypto/rust-crypto.ts
index 965c25196..e516e199f 100644
--- a/src/rust-crypto/rust-crypto.ts
+++ b/src/rust-crypto/rust-crypto.ts
@@ -135,6 +135,32 @@ export class RustCrypto implements CryptoBackend {
         return new UserTrustLevel(false, false, false);
     }
 
+    /**
+     * Finds a DM verification request that is already in progress for the given room id
+     *
+     * @param roomId - the room to use for verification
+     *
+     * @returns the VerificationRequest that is in progress, if any
+     */
+    public findVerificationRequestDMInProgress(roomId: string): undefined {
+        // TODO
+        return;
+    }
+
+    /**
+     * Get the cross signing information for a given user.
+     *
+     * The cross-signing API is currently UNSTABLE and may change without notice.
+     *
+     * @param userId - the user ID to get the cross-signing info for.
+     *
+     * @returns the cross signing information for the user.
+     */
+    public getStoredCrossSigningForUser(userId: string): null {
+        // TODO
+        return null;
+    }
+
     ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
     //
     // CryptoApi implementation