When you create a new Space, you can create a new Access Key. However, all Access Keys give you permission to access all Spaces on the account.
Please allow us to grant control which Spaces an Access Key has access to. This way you can create a new Space called "Space1", and create a new Access Key, and then tell that new Access Key it can only access Space1. If it tries to access Space2, which is also on my account, it gets a permission denied error.