relationship between primary keys and subkeys

[David Shaw]

On Jan 16, 2015, at 7:56 AM, Salih Kardan <kardan38 at gmail.com> wrote:
> 
> Hi everyone,
> 
> I have two simple questions about subkey mechanism. I search gnupg documentations and mailing list, but could not find answers to my questions. I would be so glad, if someone can answer below questions. 
> 
> 1) Is it possible to create a subkey of a subkey ?

No.  Primary keys own/parent subkeys.  There is no nesting beyond that.

> 2) What are the trust implications between a parent key and a child key? Is it "Ultimate Trust"? How can we confirm this? Or is this something for us to determine/interpret?

It's not really something that needs interpretation or calculation.  Essentially you trust a subkey exactly the same way you trust the parent key for that subkey.   The interpretation and calculation is done for the parent key.

David