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Re: [TLS] Should CCM_8 CSs be Recommended?

Sean Turner <sean@sn3rd.com> Mon, 09 October 2017 23:05 UTC

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From: Sean Turner <sean@sn3rd.com>
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Date: Mon, 09 Oct 2017 19:05:23 -0400
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Subject: Re: [TLS] Should CCM_8 CSs be Recommended?
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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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