SAN FRANCISCO — In 1970, a Stanford artificial intelligence researcher named John McCarthy returned from a conference in Bordeaux, France, where he had presented a paper on the possibility of a “Home Information Terminal.”

He predicted the terminal would be connected via the telephone network to a shared computer, which in turn would store files that would contain all books, magazines, newspapers, catalogs, airline schedules, public information and personal files.

Whitfield Diffie, then a young programmer at the Stanford Artificial Intelligence Laboratory, read Mr. McCarthy’s paper and began to think about the question of what would take the place of an individual signature in a paperless world. Mr. Diffie would spend the next several years pursuing that challenge and in 1976, with Martin E. Hellman, an electrical engineer at Stanford, invented “public-key cryptography,” a technique that would two decades later make possible the commercial World Wide Web.

On Tuesday, the Association for Computing Machinery announced that the two men have won this year’s Turing Award. The award is frequently described as the Nobel Prize for the computing world and since 2014, it has included a $1 million cash award, after Google quadrupled its size.