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Re: [TLS] Should CCM_8 CSs be Recommended?

Eric Rescorla <ekr@rtfm.com> Mon, 09 October 2017 23:11 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 09 Oct 2017 16:10:17 -0700
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To: Sean Turner <sean@sn3rd.com>
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Subject: Re: [TLS] Should CCM_8 CSs be Recommended?
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I think this text is good. I suggest "Not Recommended" with a note, and if
the IoT groups want to publish their own document updating that note, that
would work.

-Ekr



On Mon, Oct 9, 2017 at 4:05 PM, Sean Turner <sean@sn3rd.com> wrote:

> Anybody else has thoughts on this?
>
> spt
>
> > On Oct 3, 2017, at 18:53, Sean Turner <sean@sn3rd.com> wrote:
> >
> > In the IANA registries draft (https://github.com/tlswg/
> draft-ietf-tls-iana-registry-updates), we’ve added a recommended column
> to the Cipher Suites (CSs) registry (and some others).  Right now, the
> criteria for getting a recommended mark is AEAD ciphers with strong
> authentication standards track ciphers.  While that’s great generally, the
> list we’ve got five CSs that gave Joe and I pause:
> >
> > TLS_DHE_RSA_WITH_AES_128_CCM_8
> > TLS_DHE_RSA_WITH_AES_256_CCM_8
> > TLS_PSK_DHE_WITH_AES_128_CCM_8
> > TLS_PSK_DHE_WITH_AES_256_CCM_8
> > TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256
> >
> > The CCM_8 CSs have a significantly truncated authentication tag that
> represents a security trade-off that may not be appropriate for general
> environment.  In other words, this might be great for some IoT device but
> we should not generally be recommending these.
> >
> > We’re recommending that these five suites be dropped from the
> recommended list.  Please let us know what you think.
> >
> > J&S
> > (editor hats on)
>
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