Adversarial examples for fast hash functions

[Ibrahim_Mihai]

Hashing needs to be fast. xxHash boasts 60 GB/s, or basically as fast as you can read memory. Such bulk hashing is useful for file synchronisation or data integrity checking.

Many popular hashes like komihash, a5hash, HighwayHash, SpookyHash, aHash, and t1ha2 are willing to trade quality, at least for adversarial inputs, for more speed.

I was able to use Claude Fable to analyse a broad selection of popular hashes from SMhasher, a large project to empirically test statistical properties of hashes. It found that most of them have inputs on which they perform terribly—at least 20 bits below expectation.

A few hashes have published proofs, and Fable was able to find mistakes in some and verify others in Lean.
Click on any dot in the chart to read the full analysis.

https://thomasahle.com/blog/adversarial-examples-for-hashes/