phc-discussions - Re: [PHC] Re: Yarn issues

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Date: Sat, 5 Apr 2014 18:28:01 -0400
From: Bill Cox <waywardgeek@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Re: Yarn issues

On Sat, Apr 5, 2014 at 5:28 PM, Evgeny Kapun <abacabadabacaba@...il.com> wrote:
> Bill Cox <waywardgeek@...> writes:
>> If I am not mistaken, he has input collisions on both salt, and a
>> parameter called "pers".  Both are padded with 0's to 8 bytes, and
>> XOR-ed onto Blake2b state, so adding additional 0's up to a total
>> length of 8 doesn't change the output.  The password is free of such
>> collisions, so this isn't a critical issue.  He also has a spelling
>> error on the last line of his README
>
> Blake2b has exactly the same kind of collisions. Even Blake has only
> fixed-width salt.

All you have to do is hash the input lengths, and problem solved.  If
you hash all the inputs, then your algorithm gets the fun (but
misleading) label "strongly secure".

Bill