One of the inventors of the RSA algorithm (along with Adi Shamir and Len Adleman), Rivest has made ingenious contributions to making public-key cryptography useful in practice. He also invented the symmetric key encryption algorithms RC2, RC4, RC5, and co-invented RC6. The "RC" stands for "Rivest Cipher", or alternatively, "Ron's Code". (RC3 was broken at RSA Security during development; similarly, RC1 was never published.) He also authored the MD2, MD4, MD5, and MD6 cryptographic hash functions.
In 2006, Rivest published his invention of the ThreeBallot voting system, an innovative voting system that incorporated the ability for the voter to discern that their vote was counted while still protecting their voter privacy. Most importantly, this system does not rely on cryptography at all. Stating "Our democracy is too important", he simultaneously placed ThreeBallot in the public domain.
