phc-discussions - Re: [PHC] Re: Suggestion: API should include a verifier function

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Message-ID: <CACsn0c=uZ8sAh=wZs-2HLk+m-w157AV4+1ML36ZmNmCZntWmGw@mail.gmail.com>
Date: Wed, 27 Mar 2013 09:15:44 -0400
From: Watson Ladd <watsonbladd@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Re: Suggestion: API should include a verifier function

This isn't necessary: a non-constant time comparison at worst reveals the
hash, which doesn't give an attacker
enough information to break a password anyway if we do our jobs right.


On Tue, Mar 26, 2013 at 11:08 PM, Tony Arcieri <tony.arcieri@...il.com>wrote:

> On Tue, Mar 26, 2013 at 7:57 PM, Tony Arcieri <tony.arcieri@...il.com>wrote:
>
>> you'd provide a user-supplied one as input, and verify via a guaranteed
>> constant time comparison whether or not it's correct.
>>
>
> Oops, not quite what I meant to say there, but I'm sure you got the idea ;)
>
> To clarify: you would pass in the hash/salt "on file" along with the
> alleged password, and the function would return whether or not the provided
> password matches the supplied hash/salt. The arguments are, otherwise, the
> same as the hashing function.
>
> As an API strawman, if this is our hashing function:
>
>     PHS(out, outlen, in, inlen, salt, saltlen, t_cost, m_cost)
>
> we might consider:
>
>    PHS_VERIFY(hash, hashlen, in, inlen, salt, saltlen, t_cost, m_cost)
>
> (I'm not particularly married to the name "PHS_VERIFY", so please bikeshed
> away ;)
>
> --
> Tony Arcieri
>



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