Philippe Oechslin
Swiss researcher at EPFL who invented rainbow tables in 2003 and turned unsalted password hashes into a matter of seconds.
The starting point was Martin Hellman's 1980 time–memory trade-off: precompute chains of hashes, store only the start and end of each, and trade disk space for search time. Hellman's tables suffered from chains colliding and merging. Oechslin's idea, presented at CRYPTO 2003 in Making a Faster Cryptanalytic Time-Memory Trade-Off, was to use a different reduction function at every step. Two chains then merge only if they collide at exactly the same position.
His demonstration targeted Windows LM hashes and broke them in seconds, and he co-developed the free Ophcrack tool. The lasting result is really a lesson: salting makes the whole technique pointless, something Unix had done since the 1970s and Windows still didn't.