Re: [dane] Digest Algorithm Agility discussion

[Mark Andrews <[e-mail]>]

In message <[e-mail]>, Peter Palfrader writes
:
> 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?

You left out - report and refuse to send until fixed.
 
> Site B publishes both SHA2-512 and SHA1 entries.  Would you still want
> to trust SHA1?

Once you decide SHA1 is not acceptable you ignore the records with SHA1
hashes.

Publishing new hashes is trivial and will remain trivial.

Once a algorithm has reached the state where you don't trust it for a
purpose you don't use it for thar purpose.

Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
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