Miklós Ajtai
Hungarian mathematician at IBM Almaden who proved in 1996 that some lattice problems are hard on average if they are hard in the worst case – the foundation of modern lattice cryptography.
Cryptography needs randomly chosen instances to be hard, while complexity theory nearly always talks about the hardest ones. Ajtai's paper Generating Hard Instances of Lattice Problems (1996) bridged the gap: breaking a random instance would be as hard as solving every instance. Nobody had managed anything comparable for factoring or discrete logarithms.
The following year he built the Ajtai–Dwork cryptosystem with Cynthia Dwork – impractical, but important in principle. Earlier he had lent his initial to the AKS sorting network (1983) with Komlós and Szemerédi. He received the Knuth Prize in 2003.