Subj : BINKP over TLS
To   : Rob Swindell
From : Alexey Fayans
Date : Fri Dec 20 2019 09:09 pm

Hello Rob!

On Fri, 20 Dec 2019 at 09:56 -0800, you wrote to me:

 >> Isn't it your main argument against STARTTLS?
 RS> Under no case is Opportunistic TLS (e.g. STARTTLS) as secure as
 RS> Implicit TLS.

So far you didn't provide a single fact proving that good STARTTLS 
implementation is less secure than TLS on a dedicated port.

 RS> Yes, the use of self-signed certs is less secure than
 RS> CA-signed certs, but that's a different matter and true for both
 RS> Opportunistic and Implicit TLS.

Use of self-signed certs without a well-defined and implemented mandatory 
mechanism to verify these certs (either trusted CA or any other similar way) 
just turns whole security talk into a joke. Seriously.

 >> Why not? It is perfectly mitigated and I explained that a few times
 >> already. You gotta stop looking back at old SMTP implementation
 >> that wasn't designed against active MitM attacks in the first
 >> place.
 RS> I look at all the applications of Opportunistic TLS and they're all
 RS> less secure than Implicit TLS.

Examples? Maybe you are just looking at bad / not suitable implementations. Not 
all implementations are focused on MitM protection and that is fine, similar to 
use of self-signed certs just to make it a bit harder to sniff the traffic.


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