Re: MD5 is insecure

[Dan Mahoney via NANOG <nanog () lists nanog org>]

> On Sep 4, 2025, at 05:21, Tom Beecher <beecher () beecher cc> wrote:
>
> Dan-
>
> The main concern I have with your post, and the reason I have been so vocal in these messages , centers around the 
> following : 
>
> Or you might consider just going back to using inline passwords and consider Cisco’s ssh implementation a failure at 
> launch — at least the “secret” hashing algorithms are salted, but on older kit, it’s also still md5.
>
> It's absolutely fair to criticize their implementation in its current form. I could see it making sense 20 years ago, 
> but they've had time to iterate and improve on it, and should have. 
>
> However, Cisco's implementation is not vulnerable to any currently known exploits, and no theoretical attack vectors 
> don't seem to apply either. 
>
> The fact that you make a recommendation for readers to *stop using public key SSH auth* because of that is , 
> respectfully, absolutely irresponsible. Someone, somewhere is going to read this, and follow this advice, making 
> their device LESS secure, and for no good reason.  We don't tell people that current cryptography might eventually 
> someday be vulnerable to quantum computers , so stop using cryptography completely. You are doing that here, by 
> saying "This might be exploitable some day, so don't use it."  Everything MIGHT be exploitable some day, that's how 
> it goes. 

Tom,

You see those things on either sides of the words “stop using public key SSH auth” ?  Those are called quotation marks, 
and they mean, in this context, that you are directly citing my words, to the larger group.

Except that those words, in that order, appear nowhere in my article, which hasn’t changed at all, except for one typo 
which I’ve since corrected.  

I make no such recommendation.  My usage of the word “you might” is not a recommendation, it’s a statement that people 
may do their own research and carefully consider how they put an older device online, if at all.  Where you’ve cited me 
bashing md5, I am referring to its crypt() implementation, also used in Cisco type 5 secrets, matching my 
recommendations with that of the NSA.  If anything, I’ll happily suggest that the best answer for an EOL or near-EOL 
devices is “just use a serial cable”.

But back to your quote.

I believe that you’re seeing words that literally aren’t on the page, and are citing them to a public mailing list, 
claiming they’re mine.

This is not ok.

-Dan

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