Whitfield Diffie and Martin Hellman were outsiders in the field of cryptography when they devised a scheme hitherto unknown: The ability to establish secure communications over public channels between two parties that don’t know each other.
The algorithm they presented in 1976, known as Diffie-Hellman, introduced the general notion of what is now called asymmetric encryption, or public-key cryptography.
The far-ranging and long-lasting impact of this development is impossible to exaggerate. Not only is the algorithm still in use to this day, but it opened up a whole landscape of possibilities that others have expanded into. But what is the Diffie-Hellman algorithm exactly, and how does it fit into the context of online communications as it works today?