[New-bugs-announce] [issue34751] Hash collisions for tuples

[Jeroen Demeyer]

New submission from Jeroen Demeyer <J.Demeyer at UGent.be>:

It's not hard to come up with a hash collision for tuples:

>>> hash( (1,0,0) )
2528505496374819208
>>> hash( (1,-2,-2) )
2528505496374819208

The underlying reason is that the hashing code mixes ^ and *. This can create collisions because, for odd x, we have x ^ (-2) == -x and this minus operation commutes with multiplication.

This can be fixed by replacing ^ with +. On top of that, the hashing code for tuples looks needlessly complicated. A simple Bernstein hash suffices.

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messages: 325870
nosy: jdemeyer
priority: normal
severity: normal
status: open
title: Hash collisions for tuples

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34751>
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