Hash function: Difference between revisions

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Multiplicative hashing is susceptible to a "common mistake" that leads to poor diffusion&mdash;higher-value input bits do not affect lower-value output bits.<ref>

{{cite web |url=httphttps://www.cs.cornell.edu/courses/cs3110/2008fa/lectures/lec21.html |title=CS 3110 Lecture 21: Hash functions |at=Section "Multiplicative hashing"}}</ref> A transmutation on the input which shifts the span of retained top bits down and XORs or ADDs them to the key before the multiplication step corrects for this. The resulting function looks like:<ref name="fibonacci-hashing"/>

<syntaxhighlight lang="c">

unsigned hash(unsigned K) {