Re: help fuzzing/finding Horn CNF formula

[Jeff Williams <jeffwillis30 () gmail com>]

Ask Jeremy Brown, he's a pro.

http://jbrownsec.blogspot.com/



2010/2/19 Georgi Guninski <guninski () guninski com>

> i know i am dumb.
>
> i am looking for a HORN CNF that is SAT if and only if |x != y| ($x \ne y$)
> for boolean x,y.
>
> using the Horn constraints in [1] (at most k '1's) + the sought
> inequality/negation, it might be possible to encode Exact Sat (XSAT) to fast
> Horn CNF (md5 preimage falls in this case)
>
> i am not sure if such CNF formula exists though current academics claim
> Horn Sat is "P-complete", i.e. powerful enough for the formula.
>
> note that the size of the CNF doesn't matter much (it cares about just 2
> variables, the other vars are temp).
>
> i failed fuzzing it :)
>
> [1] Towards an Optimal CNF Encoding of Boolean Cardinality Constraints
> C Sinz
> http://www-sr.informatik.uni-tuebingen.de/~sinz/CardConstraints/cp2005.pdf
>
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