1977: Filing for RSA Patent
Excerpt from "RSA Public Key Encryption": U.S. Patent 4,405,829 was awarded to the Massachusetts Institute of Technology on September 20, 1983 for its "Cryptographic communications system and method." The three inventors, which the patent is named after, are Ronald Rivest, Adi Shamir, and Leonard Adleman. The patent expires 17 years from the date it was issued, Sept 21, 2000.
The RSA cryptosystem, as described in the patent, is a public-key cryptosystem that offers both encryption and digital signatures. The cryptosystem is able to encrypt and create digital signatures by taking advantage of the fact that factoring is a "hard" mathematical problem. Factoring is actually one of three commonly used "hard problems" for cryptography; the other two are the discrete logarithm problem and elliptic curves.
The RSA cryptosystem has been incorporated into popular products such as Secure Socket Layer (SSL) and Secure Shell (SSH) as well as numerous other commercial products.