# privateMapKey property Null safety

String privateMapKey
read / write

Field description: room signature, which is optional. If you want only users with the specified `userIds` to enter a room, you need to use `privateMapKey` to restrict the permission.

Recommended value: we recommend you use this parameter only if you have high security requirements. For more information, please see Enabling Advanced Permission Control.

## Implementation

    String
        privateMapKey;