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Re: [tcpm] TCP-AO crypto, SHA-2 MAC_Length (was: "Re: SHA-2 auth draft on TCP-AO")

Gregory Lebovitz <gregory.ietf@gmail.com> Wed, 08 October 2014 20:04 UTC

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Date: Wed, 08 Oct 2014 13:04:09 -0700
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From: Gregory Lebovitz <gregory.ietf@gmail.com>
To: Joe Touch <touch@isi.edu>
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Subject: Re: [tcpm] TCP-AO crypto, SHA-2 MAC_Length (was: "Re: SHA-2 auth draft on TCP-AO")
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On Tue, Sep 30, 2014 at 4:54 PM, Joe Touch <touch@isi.edu> wrote:

>
>
> On 9/30/2014 4:19 PM, Gregory Lebovitz wrote:
> ...
> > GML>  we clearly didn't say "MUST be 96 bits, no more", but the last
> > sentence was meant to guide people toward a truncation of the MAC down
> > to 96-bits in order to fit nicely into the -AO option field.
>
> The -AO option supports any MAC length. The issue is conservation of TCP
> header option space and its interaction with other TCP options.
>

+1, good clarification


>
> > There was
> > security review and consensus that truncating a MAC output > 96 bits
> > would be fine.
>
> "fine" was determined at the time by both Security and Transport, i.e.,
> Security felt it was large enough for the desired protection and
> Transport felt it was small enough to "play nice" with other options.
>

+1
Gregory


>
> Joe
>



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