Re: [OAUTH-WG] MTLS vs. DPOP

I don't see them the same at all. With MTLS, the token is bound to the 
transport layer (and the key used to establish that encrypted 
connection). With DPOP, the token is bound to the private key known to 
the client.

To compromise an MTLS bound token the attacker has to compromise the 
private key. To compromise a DPOP bound token, depending on what HTTP 
request elements are signed, and whether the DPOP is managed as 
one-time-use etc, there are additional attacks. (Ducks head and waits 
for all the real security experts to prove me wrong:)

The deployment models are also different. With MTLS bound tokens the 
clients don't really have to know about the binding because it is 
established at the AS and the deployment of the service manages the cert 
used for the MTLS connection. This is simpler for client development 
(provided the environment is already set up for MTLS everywhere).

I'd strong encourage us to continue supporting both methods.

On 5/7/19 4:25 AM, Hannes Tschofenig wrote:
>
> Hi all,
>
> In the OAuth conference call today Vittorio mentioned that some folks 
> are wondering whether DPOP is essentially a superset of MTLS and 
> whether it makes sense to only proceed with one solution rather 
> potentially two.
>
> I was wondering whether others in the group have a few about this aspect?
>
> Ciao
>
> Hannes
>
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