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<div class="moz-cite-prefix">On 11/19/20 2:46 AM, Phillip
Hallam-Baker wrote:<br>
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cite="mid:CAMm+Lwj-uiM_G4=fmUi4iZBW72cnmV1KTAPiOMrE6uqUyzg9Gg@mail.gmail.com">
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<div class="gmail_default" style="font-size:small">Sure, nobody
leaves the front door open on the password file any more. But
breaches occur regularly and the password files leak... <br>
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<p>You are optimizing for a very specific case: <br>
</p>
(1) A site uses password hashes, <br>
(2) for passwords that are allowed to be long, <br>
(3) and are honored in their entire length*, <br>
(4) is broken into and they don't tell me,<br>
(5) the breakin doesn't include general admin powers but just
supplies that one file,<br>
(6) the attacker bothers to crack the hash for my password, and<br>
(7) it does any good for the attacker to have that password.<br>
<p>* Even Linux is willing to let you use long passwords where
anything past 8-characters are quietly ignored—if you set things
up wrong. I've twice discovered this where I didn't set it up that
way, a system installation script did.<br>
</p>
If I don't recycle passwords, getting all the way to #7 lets the
attacker impersonate me only on this one iffy site, which the
attacker already has some backdoor access to. By insisting on
unmanageably long passwords for everything, you do avoid this one
narrow circumstance.<br>
<p>But there are a lot of ways for people to get security wrong, by
the time they let their password data leak you need to assume
things are very broken. <br>
</p>
<p>What makes you think there is any hashing going on at random
site? <br>
</p>
<p>I have a large collection of plain-text passwords that have
publicly leaked, where did I get those? That doesn't smell like
hashing to me. Why do so many sites have password length and
severe password content restrictions? That doesn't smell like
hashing to me.<br>
</p>
As long as my password even approaches a couple dozen-ish bits of
real entropy, if I haven't given away copies (by recycling), my
password is not going to be the weak link.<br>
<br>
<p>Do you have an ATM card? Well, if someone finds a way into your
bank's computers that isn't via your PIN, then it didn't happen
because your PIN was too short. And if you have to change your PIN
as part of the cleanup, your new one doesn't have to be any longer
than was your old one. The PIN wasn't the problem.</p>
<p><br>
</p>
<p>By telling people that every password has to be unmanageably
long, you are effectively discouraging people from using difficult
passphrases when it really does matter: for encryption.</p>
<p> <br>
</p>
<p>-kb<br>
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