Chronicle No. 39 · Innovations

32 Holes in a Piece of Plastic: The Lock That Forgets

A Norwegian engineer read about an attack on a hotel guest and built a lock that changes its mind at every checkout.

The metal room key had one incurable flaw. It never expired. Copies drifted into pockets and drawers and the hands of people who had checked out months earlier, and a genuinely lost key meant a locksmith or a lie.

Tor Sornes (1925-2017) ran research and development at a factory in Moss, Norway that made locks and ice skates under the brand Ving. What pushed him into action was a guest-safety failure that shook the industry: in 1974, a hotel guest was attacked by an intruder who entered through a door that appeared to be locked. The resulting negligence case, Garzilli v. Howard Johnson's Motor Lodges, produced a landmark verdict in 1976 and put guest-room security on the agenda of every operator in the world.

Sornes's answer was mechanical and elegant. A plastic card punched with 32 holes, yielding roughly 4.2 billion possible combinations. The crucial part was not the card but the lock: it was recodable, so issuing a new card silently killed the one before it. Accounts differ on the exact launch year, with most Norwegian sources giving 1975 and others 1977, but the system was patented in 29 countries and United States patent 4,149,394 was granted on 17 April 1979.

Its proving ground was the Peachtree Plaza in Atlanta in 1978, then the tallest hotel in the world, which fitted the locks throughout.

Every tap of a card or a phone against a door today rests on the same idea. Not a stronger barrier, but a lock that forgets the last guest the moment the next one arrives.

Lesson: Real security is not a harder barrier but a credential that expires, and the time to build it is before an incident forces you to.