Charles Bennett, The Physicist Who Made Eavesdropping Impossible To Hide

He spent a decade proving that computing need not destroy anything, and then built two of the strangest useful things in physics out of what he learned. In 1984 a physicist at IBM and a computer scientist in Montreal published a protocol for sharing a secret key, at a conference in Bangalore, in proceedings that were for years genuinely difficult to obtain. It described a way for two people who had never met to agree on a string of random bits, and to know for certain whether anyone had listened in. The security did not rest on any assumption about how much computing power an eavesdropper had. It rested on the fact that measuring a quantum system disturbs it. Forty-one years later, in 2025, that paper won…