one less onion skin

[Steve Southam]

I'm not sure if this really happens, but if you have a connection open 
to an OR and a new circuit is required through it,
couldn't ORn-1 send a CREATE_FAST to ORn?


> Steve Southam wrote:
>> Is it because the ORs don't know where they are in the circuit?
>> Of course OR3 knows it's at the end, but the others either recognize 
>> or relay.
>
> I agree that not using k_1, d_1 would allow OR1 to determine that they 
> are the first node in a circuit.  However, Tor clients already leak 
> this information.  The key agreement with OR1 is done using a 
> "CREATE_FAST" command rather than a normal "CREATE".  So, once an OR 
> receives a "CREATE_FAST" it knows its position in the circuit. (it 
> might be that Tor clients which are also onion routers themselves do 
> not send "CREATE_FAST"... I am not sure)
>
> So the question is, if we have already leaked this information, are we 
> wasting CPU cycles doing AES with OR1?
>
> -James
>