[issue13703] Hash collision security issue

M.-A. Lemburg mal at egenix.com
Mon Jan 9 13:16:09 CET 2012

Marc-Andre Lemburg wrote:
> Marc-Andre Lemburg <mal at egenix.com> added the comment:
> Christian Heimes wrote:
>> Marc-Andre:
>> Have you profiled your suggestion? I'm interested in the speed implications. My gut feeling is that your idea could be slower, since you have added more instructions to a tight loop, that is execute on every lookup, insert, update and deletion of a dict key. The hash modification could have a smaller impact, since the hash is cached. I'm merely speculating here until we have some numbers to compare.
> I haven't done any profiling on this yet, but will run some
> tests.

I ran pybench and pystone: neither shows a significant change.

I wish we had a simple to run benchmark based on Django to allow
checking such changes against real world applications. Not that I
expect different results from such a benchmark...

To check the real world impact, I guess it would be best to
run a few websites with the patch for a week and see whether the
collision exception gets raised.

Marc-Andre Lemburg

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