Ronald Cramer
Dutch cryptographer who, with Victor Shoup, proved that practical encryption can resist chosen-ciphertext attacks without leaning on random oracles.
Through the 1990s there were two kinds of public-key encryption: schemes with security proofs that were too slow to use, and fast schemes whose proofs required treating the hash function as an idealised random oracle. Cramer–Shoup (1998) was the first to be both efficient and provably IND-CCA2 secure in the standard model, assuming only that decisional Diffie–Hellman is hard.
Earlier, with Ivan Damgård and Berry Schoenmakers, he had shown how to prove knowledge of one of several secrets without revealing which — a building block in many later voting protocols. He has worked at CWI in Amsterdam and at Leiden University, and in 2015 published the textbook Secure Multiparty Computation and Secret Sharing with Damgård and Jesper Buus Nielsen.