“New Directions in Cryptography” by Whitfield Diffie and Martin E. Hellman was published in the IEEE Transactions on Information Theory in November 1976. A copy hosted on Hellman’s own Stanford publications page carries both authors’ names. It is the founding document of public-key cryptography.
The paper opens by arguing that the widening applications of teleprocessing had created a need for new types of cryptographic systems. The two needs it set out to meet were minimizing the requirement for secure key distribution channels and supplying the equivalent of a written signature for electronic communication.
To address the first need, the authors introduced public key distribution, a way for two parties to agree on a shared secret key over a public channel without having met or exchanged secret material beforehand. This is the construction now known as Diffie-Hellman key exchange. To address the second, they described public-key cryptosystems and the concept of a digital signature, in which a publicly known key can be used to verify a message that only the holder of a private key could have produced.
The paper reframed cryptography from a discipline of shared secrets into one in which strangers could communicate securely, and it set the agenda for the public-key systems, including RSA, that followed within a few years.