private Task <FileOperationContext> EncryptionUpgradeWorkAsync(IDataStore store, IProgressContext progress)
        {
            FileOperationsController operationsController = new FileOperationsController(progress);

            operationsController.QueryDecryptionPassphrase = HandleQueryDecryptionPassphraseEventAsync;

            operationsController.KnownKeyAdded = new AsyncDelegateAction <FileOperationEventArgs>(async(FileOperationEventArgs e) =>
            {
                await _knownIdentities.AddAsync(e.LogOnIdentity);
            });

            return(operationsController.EncryptionUpgradeAsync(store));
        }