[Cryptography] How widely are the PSK modes used?

Jon Callas jon at callas.org
Thu Feb 21 18:22:16 EST 2019



> On Feb 21, 2019, at 10:30 AM, Dmitry Belyavsky <beldmit at gmail.com> wrote:
> 
> чт, 21 февр. 2019 г., 21:27 John Denker <jsd at av8n.com>:
> On 2/21/19 2:48 AM, Dmitry Belyavsky wrote:
> 
> > Could you please describe the spheres where PSK ciphersuites are used in
> > practice?
> 
> You mean besides more-or-less every WPA wireless setup?
> 
>  Does WPA use TLS? I mostly mean TLS context. Sorry for the lack of clarity. 

I think this gets to the core of the issue. As John Denker points out, just about every WiFi setup in the world is using a single pre-shared key. You can get per-link keys, but you have to set up “Enterprise” WPA and do Radius and stuff like that. It’s much easier to have a PSK and go.

In contrast, TLS is *easy* to use with ephemeral(ish) keys; it’s the usual way we all do it. You *can* do TLS with PSKs, but it’s hard to set up. Thus, you rarely see PSK with TLS for the very same reason you usually see it with WPA.

Thus, I’m curious about what the question behind your question is. In TLS, it’s hard to set up PSKs, it’s not the normal user experience, and consequently it’s rare. If it were easy to use PSKs with TLS, we’d see it a lot. 

	Jon



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