phc-discussions - Re: [PHC] A silly (?) consideration for script-friendly hashes

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Date: Fri, 24 Jan 2014 14:41:59 -0800
From: Larry Bugbee <bugbee@....com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] A silly (?) consideration for script-friendly hashes

On Jan 24, 2014, at 2:29 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On Fri, Jan 24, 2014 at 2:20 PM, Larry Bugbee <bugbee@....com> wrote:
>> On Jan 24, 2014, at 2:17 PM, Andy Lutomirski <luto@...capital.net> wrote:
>>> On Fri, Jan 24, 2014 at 2:16 PM, Larry Bugbee <bugbee@....com> wrote:
>>>> On Jan 24, 2014, at 2:13 PM, Andy Lutomirski <luto@...capital.net> wrote:
>>>> 
>>>>> just hash the domain in
>>>>> with the salt before using it to hash a password
>>>> 
>>>> Good idea, but why not also add userid?
>>>> 
>>>> 
>>> 
>>> Because then you need some kind of trusted input so that scripts can't
>>> just fake the userid.
>> 
>> Sorry, and perhaps I'm dense, but I don't see why that's a problem.
>> 
> 
> If the API is Hash(userid, domain, salt, password), then the browser
> can only really verify "domain".  How is it going to check that
> "userid" is correct?

Why would it need to if it knew the userid fm the login fields?  Perhaps we are talking abut two different problems?  

I was thinking the kitten processors would be working on new dictionaries and adding the domain to the hash which would be a good way to cause the attacker to have to generate a fresh set of dictionaries for each site.  Fine, but if you add userid (converted to lower/upper case to avoid server mismatches) to the hash they would need a dictionary for each user at that site.  ...or at a minimum, they would have to discover the userid for the victim.  

Are you thinking of a different use case?

> --Andy
> 
>> 
>>> At that point, you might as well try to use a
>>> protocol like SRP instead.
>>> 
>>> --Andy
>> 
> 
> 
> 
> -- 
> Andy Lutomirski
> AMA Capital Management, LLC