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Re: [dane] Digest Algorithm Agility discussion

Peter Palfrader <peter@palfrader.org> Sun, 23 March 2014 19:10 UTC

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Date: Sun, 23 Mar 2014 20:10:37 +0100
From: Peter Palfrader <peter@palfrader.org>
To: dane@ietf.org
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References: <20140315051704.GY21390@mournblade.imrryr.org> <0l4n2sa5a0.fsf@wjh.hardakers.net> <20140322074737.GA5739@anguilla.noreply.org> <20140323174205.63C6111B2111@rock.dv.isc.org> <20140323182106.GX24183@mournblade.imrryr.org> <20140323185718.7A84711B2CB8@rock.dv.isc.org>
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Subject: Re: [dane] Digest Algorithm Agility discussion
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On Mon, 24 Mar 2014, Mark Andrews wrote:

> If you don't trust a algorithm you should not be using it.  Period.
> This fall back to this untrusted/broken algorithm is bad engingeering
> and bad security practice.
> 
> If the site you want to email only has broken TLSA records, get
> them on the phone to fix the problem.

Assume we may have reason to believe that SHA1 is within reach of well
funded adversaries, and assume it had a code-point in DANE.

Site A only publishes SHA1 entries.  Would rather do unauthenticated TLS
than trust SHA1?

Site B publishes both SHA2-512 and SHA1 entries.  Would you still want
to trust SHA1?

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