In September of 1974, when he was 30 years old, Whitfield Diffie was obsessed with cryptography. So obsessed that he was criss-crossing the country trying to talk to anyone who could help him expand his ideas. He'd moved to California a few years before to work at a Stanford artificial intelligence lab, and, in the end, it was at Stanford where he found Martin Hellman. Hellman would later describe that meeting to the journalist Stephen Levy as "an immediate meeting of the minds." Within two years the two men would speed towards "the brink of a revolution in cryptography." And in 1976 they published the paper describing public key cryptography—a system used in everything from Blackberries to financial transactions.

The idea of public-key cryptography is surprisingly simple. For centuries, codes depended on private keys—the secret to translating information into code and back out again, into a readable form—that had to be agreed on before information was sent from one person to another. The problem was that, somehow, both parties needed to get ahold of the key. Often that meant having a courier shuttle it around. The system that Diffie and Hellman described solved that problem by splitting the key in two, a public key and a private key.