Re: [TLS] TLS 1.3 Problem?

Watson Ladd <watsonbladd@gmail.com> Tue, 29 September 2020 00:38 UTC

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From: Watson Ladd <watsonbladd@gmail.com>
Date: Mon, 28 Sep 2020 20:38:05 -0400
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To: "Michael D'Errico" <mike-list@pobox.com>
Cc: TLS List <tls@ietf.org>
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Subject: Re: [TLS] TLS 1.3 Problem?
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On Mon, Sep 28, 2020 at 6:33 PM Michael D'Errico <mike-list@pobox.com> wrote:
>
> On Mon, Sep 28, 2020, at 11:07, Hannes Tschofenig wrote:
> >
> > Luckily, we don't have any angry cryptographers in this group.
>
> Were they all pushed away too?
>
> Anyway, back on the topic of stateless HelloRetryRequest, I
> don't see how this can work given that the client can make
> several modifications to the ClientHello which will invalidate
> the hash sent in the "cookie" (even if the client echos it back
> as required without modification).

The hash isn't used for validation, but for continuing the running
hash of the transcript to ensure that the negotiation isn't interfered
with. See section 4.4.1.

>
> Is stateless HelloRetryRequest even being used?  If so, how?

QUIC depends on it iiuc.

Sincerely,
Watson

-- 
Astra mortemque praestare gradatim