MD5 considered harmful

Zaid Ali zaid at
Sat Jan 28 00:04:49 UTC 2012

I am in the camp of no MD5 in general and more specifically IX. It is a
real pain to manage MD5 and no network in my experience has ever
implemented a sustainable solution. There is no BCP that folks follow so
generally its a verbal agreement that someone in either party will
maintain the record. This works until that operator leaves the job and the
MD5 is in their email box which is no longer accessible. I would say this
is pretty common, I have inherited quite a few networks where I had to
deal with this problem. Also most common places where people store MD5's
are not in secure locations. I would argue that even though you connect
via shared medium in the case of an IX you can still use TTL.


On 1/27/12 3:20 PM, "Jared Mauch" <jared at> wrote:

>On Jan 27, 2012, at 3:52 PM, Patrick W. Gilmore wrote:
>> Your network, your decision.  On my network, we do not do MD5.  We do
>>more traffic than anyone and have to be in the top 10 of total eBGP
>>peering sessions on the planet.  Guess how many times we've seen anyone
>>even attempt this attack?  If you guessed more than zero, guess again.
>> I am fully well aware saying this in a public place means someone,
>>probably many someones, will try it now just to prove me wrong.  I still
>>don't care.  What does that tell you?
>I would generally say: If you are on a p2p link or control the network,
>then yeah, you don't need md5.  If you are at a shared medium (e.g.: IX)
>I do recommend it there, as it will help mitigate cases where someone can
>hijack your session by putting your IP/ASN whatnot on the router.
>The threat (Attack) never became real and we've now had enough time that
>even the slowest carriers are running fixed code.
>- Jared

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