How can the secure storage be secure?

How can the secure storage be secure?

1. Does any storage can be access stand alone?

2. If it is be encrypted, but where to save the key in secure?

3. Is some storage also have Secure and Non-secure mode?

Thanks

Secure data ,like the key, can be stored in secure flash memory or some other secure memory.
Right now, that is not supported and that would be implemented in the future.