Re: [TLS] Should CCM_8 CSs be Recommended?

How much of a problem with people are we going to get into if the IoT profiles for the IETF go and say "You MUST use this algorithm which the IETF does not recommend?"

I think that this is very likely to get some strong push back from people I that is the case.  Reluctantly I think that we need to keep the recommendation on this algorithms.

> -----Original Message-----
> From: TLS [mailto:tls-bounces@ietf.org] On Behalf Of Sean Turner
> Sent: Tuesday, October 3, 2017 3:54 PM
> To: <tls@ietf.org> <tls@ietf.org>
> Subject: [TLS] Should CCM_8 CSs be Recommended?
> 
> 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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