Erlang hash-dos review.
TLDR. It's easy to generate collisions for phash and phash2 when hashing binaries. Erlang dict uses phash so if its possible to generate quadratic slow down by triggering collisions. ETS uses phash2 so its possible to generate quadratic slow down by triggering collisions in ETS. The good news is that even though erlang maps uses phash2 and its possible to generate collisions it does not seem easy to trigger a quadratic slow down because the hash array mapped trie implementation rehashes the input with a different prefix when it can't find a unique position in the trie and it looks like it is difficult to generate inputs that collide over multiple different prefixes.
This review is going to focus on taking the hash of binaries because this is the most likely user controllable input to the hash functions.