

Bloom Filters - biesnecker
http://www.jasondavies.com/bloomfilter/

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w8rbt
I actually implemented a bloom filter once to audit passwords in the 'real-
world'.

We had a user who wanted a password audit, but who refused to provide password
hashes. He insisted the hashes were too sensitive to give to anyone outside
his organization.

So we wrote the bloom filter program and showed him how to run it. Its output
was a... bloom filter (a C++ std::bitset<>.to_string()) that we could take and
compare against known common hashes. Easy to compress. He liked the fact that
it was just ones and zeros. No hashes were given to us. Just a string of ones
and zeros. Not that there's a difference really.

Anyway, we took his filter and compared it to known weak hashes and when any
known weak hash matched, we added that to another filter that we created and
sent that back to him and he would make one final pass (using the new filter)
to show the weak user name, password, etc.

No password hashes were ever exchanged and it worked OK. We uncovered many
weak passwords. He seemed happy. However, the test/audit was not as thorough
as I would have liked. You're limited without hashes and this approach is pre-
compute intensive.

So there you have it. Bloom filters in the wild and in use. I still have the
code someplace. All standard C++ and Crypto++.

~~~
biesnecker
That's an awesome story. Thank you for sharing.

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pradn
Bloom filters and genetic algorithms seem to be subjects of perennial tutorial
articles on Hacker News and /r/programming. They're easy enough to understand
with a background in the classically-taught data structures and algorithms.
Yet, they're usually not covered in many courses, so they're still novel.

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valarauca1
[https://www.youtube.com/watch?v=-SuTGoFYjZs](https://www.youtube.com/watch?v=-SuTGoFYjZs)

Linked is an excellent video talking about bloom filters. Done is a slightly
comical style. Very informative, slightly funny.

Author's Site is Cube-drone.com a rather amusing comic about the day-to-day
life of a java developer form the perspective of a java developer.

~~~
hobofan
Thanks for linking the authors site! I loved his youtube videos, but didn't
know he also does web comics.

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Sir_Cmpwn
Bloom filters seem like the big thing to write blog posts about now.

[https://hn.algolia.com/?q=bloom+filter#!/story/forever/0/blo...](https://hn.algolia.com/?q=bloom+filter#!/story/forever/0/bloom%20filter)

~~~
dionidium
They pop up over and over again. The first wave of popularity I'm old enough
to remember was back in '04 [0]

[0]
[http://www.perl.com/pub/2004/04/08/bloom_filters.html](http://www.perl.com/pub/2004/04/08/bloom_filters.html)

