1976: Diffie and Hellman presented public-key exchange idea.
NOTE - in 2016, Whitfield and Diffie were awarded the 2015 "Nobel Prize of Computing," - the ACM - Association for Computing Machinery's 2015 A.M. Turing Award for critical contributions to modern cryptography. Their invention of public-key cryptography and digital signatures revolutionized computer security. Learn more about their contributions and their award via the link included below.
Diffie–Hellman key exchange (D–H) is a specific method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as originally conceptualized by Ralph Merkle. D–H is one of the earliest practical examples of public key exchange implemented within the field of cryptography. The Diffie–Hellman key exchange method allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure channel. This key can then be used to encrypt subsequent communications using a symmetric key cipher.