phc-discussions - Re: [PHC] Terminology goals

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Message-ID: <op.w14w4qnuyldrnw@laptop-air>
Date: Tue, 20 Aug 2013 14:39:52 -0700
From: "Jeremy Spilman" <jeremy@...link.co>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: Re: [PHC] Terminology goals

I agree it's useful for us to have some general knowledge of the hashing  
function / work factor that was in place. I think the best place for this  
is inside a published privacy policy, and it would be great if this became  
expected / established practice. Companies avoid this by claiming they  
want to keep it secret, which we know is always useless, and often harmful.

For communicating a breach to end users, I think any mention of hashing  
misses or even obfuscates the key point. The major thrust of any breach  
notification should be that the user's password is "lost" and that they  
should never use that password, on any site, ever again.

Once an attacker has all the data required to run an offline attack,  
successful password cracking will always be a function of password  
complexity and hashing complexity. In a highly simplified view of 'weak'  
and 'strong' passwords, and 'weak' and 'strong' hashing functions, you  
would need both strong passwords with strong hashing to defend against a  
short-term offline attack.

To put it another way, no amount of hashing complexity can protect a weak  
password from an offline attack. And most passwords are weak.

The biggest problem I see with the current crop of breach notifications is  
the "This means that the password files are unreadable" part. This is not  
actually true, and using scrypt or bcrypt or even PHC-Finalist-X doesn't  
make it true. Companies are hiding behind hashing, when they should be  
admitting that "Most password data breaches result in the vast majority of  
users' passwords being exposed."
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