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

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Date: Fri, 24 Jan 2014 14:51:53 -0800
From: Andy Lutomirski <luto@...capital.net>
To: discussions <discussions@...sword-hashing.net>
Subject: Re: [PHC] A silly (?) consideration for script-friendly hashes

On Fri, Jan 24, 2014 at 2:41 PM, Larry Bugbee <bugbee@....com> wrote:
> 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?

Yes.  I'm thinking that the kitten site would only be able to compute
hashes with domain = "kittens.com" (or maybe "anything.kittens.com")
and not, say, "whitehouse.gov".

--Andy