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Re: [TLS] Should CCM_8 CSs be Recommended?

Eric Rescorla <ekr@rtfm.com> Wed, 04 October 2017 02:55 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 03 Oct 2017 19:54:42 -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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Generally I tend to agree we should remove these, but as Jim said, there
are reasons where I guess they make sense. Could we add a "Special
Circumstances" marking?

-Ekr


On Tue, Oct 3, 2017 at 3:53 PM, 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)
> _______________________________________________
> TLS mailing list
> TLS@ietf.org
> https://www.ietf.org/mailman/listinfo/tls
>

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