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Re: [Secdispatch] Oblivious HTTP charter draft

Eric Rescorla <ekr@rtfm.com> Sat, 20 March 2021 22:59 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Sat, 20 Mar 2021 15:58:42 -0700
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To: Benjamin Kaduk <kaduk@mit.edu>
Cc: Martin Thomson <mt@lowentropy.net>, IETF SecDispatch <secdispatch@ietf.org>
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Subject: Re: [Secdispatch] Oblivious HTTP charter draft
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On Sat, Mar 20, 2021 at 3:35 PM Benjamin Kaduk <kaduk@mit.edu> wrote:

> On Thu, Mar 18, 2021 at 12:24:33PM +1100, Martin Thomson wrote:
> [...]
> > The OHTTP working group will define the Oblivious HTTP protocol, a
> method of encapsulating HTTP requests and responses that provides
> protected, low-latency exchanges. The working group will define any
> encryption scheme necessary and supporting data formats for carrying
> encapsulated requests and responses, plus any key configuration that might
> be needed to use the protocol.
>
> What does it mean to "define an[y] encryption scheme"?
>

I believe this just means "data format".


> The OHTTP working group will include an applicability statement that
> documents the limitations of this design and any usage constraints that are
> necessary to ensure that the protocol is secure.
>
> Is this intended to be an Applicability Statement as defined in RFC 2026?
>
> > The working group will define a format for any encryption keys that are
> needed. The working group will not describe how encryption keys are
> obtained. The working group will not define any methods for discovering
> proxy or server endpoints; specific uses of the protocol will need to
> describe discovery methods or rely on configuration.
>
> Why do we need new formats for encryption keys?  Don't we already have a
> bunch of those?  Defining how to obtain keys is necessary, of course.
>

What you need is actually more like a format for defining the complete
parameter space that the server accepts (key, HPKE algorithm, etc.)
Effectively what's in HPKEConfig:

https://tlswg.org/draft-ietf-tls-esni/draft-ietf-tls-esni.html#name-encrypted-clienthello-confi

-Ekr



> Thanks,
>
> Ben
>
> > The OHTTP working group will work closely with other groups that develop
> the tools that OHTTP depends on (HTTPbis for HTTP, CFRG for HPKE) or that
> might use Oblivious HTTP (DPRIVE for DNS over HTTPS).
> >
> > The working group will use draft-thomson-http-oblivious as input.
> >
> > _______________________________________________
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