Re: Stateful compression of cookies (Re: Delta Compression and UTF-8 Header Values)

On Mon, Feb 11, 2013 at 10:05 AM, Phillip Hallam-Baker <hallam@gmail.com> wrote:
> On Mon, Feb 11, 2013 at 10:24 AM, Nico Williams <nico@cryptonector.com>
> wrote:
>> (Also, a note about small session IDs: they can't be so small as to be
>> guessable.  32-bit session IDs would be a disaster.  I think I'd not
>> feel comfortable with session IDs smaller than 96-bits.)
>
>
> Please, lets not repeat the mistake of doing bearer tokens.

Heh, well, you know that I'm with you on this, as we both have I-Ds
that involve the use of MACs to authenticate access to sessions on
each request.

> I would very much like to separate out authentication tokens from state
> tokens so that we can get some sanity. But the replacement for the use of a
> session cookie for authentication should be a proof of knowledge of the
> shared secret rather than presentation of the shared secret itself.

Right.

> Doing this would render the various BEAST and CRIME attacks ineffective
> along with most cookie stealing as the  confidential data would only go
> across the wire in plaintext at most once.

Although BEAST/CRIME are not the only reasons to want this.

> So the communication pattern might be:

But we still need a) a session ID, and/or b) server-side state stored
as encrypted cookies (in the generic sense, not "web cookies") on the
client side.

Nico
--

Received on Monday, 11 February 2013 16:37:26 UTC