Ron Rivest
lorecryptographysecurity
The R in RSA: co-author of the 1977 paper that turned public-key cryptography from a proposal into something implementable, and joint recipient of the 2002 Turing Award.
Diffie and Hellman had described what was needed and said plainly that they had no realistic way to build it. Rivest, with Shamir and Adleman at MIT, produced one within a year, and the trio founded RSA Data Security in 1982 - which is how the algorithm reached the products rather than the journals. The Turing citation is precise about the contribution: making public-key cryptography useful in practice. He also wrote the MD and RC families of algorithms, several of which the field later had to retire.
Also known as: rivest, rsa