[Cryptography] Toxic Combination

Alfie John alfiej at fastmail.fm
Sun Nov 30 17:58:25 EST 2014

On Mon, Dec 1, 2014, at 08:55 AM, Guido Witmond wrote:
> I'm starting to consider the combination of current best practice with
> server certificates and password to be a Toxic Combination.
> The general issue is twofold:
>     People need to validate the authenticity of a site before typing in
> their password;
>     The password gets transmitted to the other party.

And this is taken advantage of every day by phishing attacks. However
although your solution of setting up DNSSEC and DANE is the _correct_
solution, it's just too complex and hard to get right for a lot of
system admins so it's not going to get uptake - just look at how PGP is
also the _correct solution_ for encrypting messages and yet has not had
the uptake since 1991!

I think a better solution would be something like implementing Digest
Authentication (RFC 2069, but replacing MD5 with something like AES-256
and allow it to be upgradable) in the browser. The password field value
would then be replaced with the value from the DA call and no secrets
would be leaked. This solution would get way faster adoption.


> Most people assume that if it looks like their bank and the address bar
> is green then it should be safe. Regrettably, it’s not. Criminals obtain
> valid certificates using stolen creditcards and passports. The true
> method for authenticating a site requires verification of server
> certificate fingerprints. And if you don’t know what that means, you
> have to spot the spelling errors, the differences in layout and other
> mistakes to detect the scammers. Good luck!
> The second part is just as problematic: The password must remain secret,
> yet it must be transmitted to the other side to log in.
> This is the Toxic Combination. One failure to detect a scammer’s site
> and the password is compromised. The scammers can do everything that you
> can do with the password.
> [promo]
> For more information, please see:
> http://eccentric-authentication.org/blog/2014/11/30/spot-the-differences.html
> http://eccentric-authentication.org/Usable-Security.pdf
> [/promo]

  Alfie John
  alfiej at fastmail.fm

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