Adversarial examples for fast hash functions: how Claude Fable broke SMHasher favorites
thomasahle · x · 2026-09-20
Blog post detailing how thomasahle used Claude Fable to find adversarial collisions in popular fast hash functions.
- Key claim: passing statistical tests says nothing about attacker-chosen input collisions, even when the seed stays secret. xxHash-class hashes run at 60 GB/s, but komihash, a5hash, HighwayHash, SpookyHash, aHash, and t1ha2 trade adversarial robustness for speed.
- Framework: b-bit universal hashing bounds collision probability at L·2^-b — a rare provable guarantee in cryptography; the open question is the fastest possible hash at a given b.
- Method: Fable analyzed popular SMHasher hashes and produced collision inputs (code, data, and verification published), showing agent swarms can systematically probe weak hashes.
Related event: Claude Fable Breaks Multiple Fast Hash Functions in a Day(2 posts)→
More from Safety
- Why do major labs trust Irregular for security while it keeps appearing in model hacks? — almmaasoglu · 2026-09-20
- Sarcastic take mocks AI labs: models 'too dangerous to release' wired to automated P4 virus lab — IgorCarron · 2026-09-20
- Venkatesh Rao: EA Promised to Solve AI Safety — Now We Have Two Problems — round · 2026-09-20
- From physics to AI: capability without control means rising systemic risk — AryHHAry · 2026-09-20
- Bug bounty debate gets speedrun as AI model hacking incidents pile up — HackingLZ · 2026-09-20
- Plugin4Shell zero-click RCE hits Claude Code, Codex, Copilot and Gemini CLI days before NIST IR 8587, exposing the gap in agent authorization — docybo · 2026-09-20