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Re: [TLS] Closing on 0-RTT

Eric Rescorla <ekr@rtfm.com> Mon, 26 June 2017 18:16 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 26 Jun 2017 11:16:02 -0700
Message-ID: <CABcZeBPsAv8t14rEfdW1QRbSZenBTHixR-tSo+4hbyV3VMbkEw@mail.gmail.com>
To: Colm MacCárthaigh <colm@allcosts.net>
Cc: Ilari Liusvaara <ilariliusvaara@welho.com>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Closing on 0-RTT
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OK, I'll move this out of the "if you can do a lot of replays" section

On Mon, Jun 26, 2017 at 10:25 AM, Colm MacCárthaigh <colm@allcosts.net>
wrote:

>
>
> On Sun, Jun 25, 2017 at 11:43 PM, Ilari Liusvaara <
> ilariliusvaara@welho.com> wrote:
>
>> I understood that the cache probing attack requires much less replays
>> than the other side-channel ones. And furthermore, distributing the
>> replays among zones makes the attack easier (because replay with the
>> cached data hot doesn't tell that much).
>>
>
> In practice with real world HTTP caches, one replay is often sufficient.
> That's because in addition to the faster load time you can look at the
> cache headers (like max-age) to pinpoint that it was the replay that put
> the item in the cache. This would work with DNS too, where TTL or RRSET
> cycling leaks more information in the same way.
>
> Using more zones does help, and if the attacker were targeting a busy
> cache, then it can certainly help to weed out the noise and increase the
> likelihood of finding a zone/node where the cache is empty to begin with.
>
> --
> Colm
>

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