How Hollywood's Hedy Lamarr Designed a Warproof Communications Tool

Hedy Lamarr. Source: hedylamarr.org

Hedy Lamarr. Source: hedylamarr.org

Today is Hollywood actor Hedy Lamarr’s 101st birthday. It is being celebrated not only by movie fans but telecom engineers all over the world. Why could that be?

Hedy Lamarr was born Hedwig Eva Marie Kiesler, and hit headlines as an actress with a nude swimming scene in her Czech film Ecstasy (1933). She later married a rich, pro-Nazi arms merchant named Fritz Mandl, to whom she was a trophy wife. Mandl took Lamarr along to many parties and dinners to socialise with the high and mighty of politics, and the military of Europe. Little did he suspect that beneath Lamarr’s beautiful exterior lay a unique aptitude for technology, and that she was able to pick up quite a bit of the technical shop-talk of the men around the table.

When the war began, Lamarr, a staunch anti-Nazi, escaped to London where she convinced Louis Mayer of MGM Studios to sign her up. Mayer, having heard of her reputation after Ecstasy, advised her to change her name from Hedwig Kiesler to Hedy Lamarr and to act in “wholesome family movies”, which she promptly agreed to.

As the war progressed and the US got involved, Lamarr informed the American government that she was privy to considerable amount of Axis war technology and that she wanted to help. The Defence Department had little faith in her claims and instead advised her to sell war bonds. However, Lamarr was unrelenting; along with her friend George Antheil, an avant-garde composer and musician, she patented their new communications system in 1941 and gave the patent rights for free to the US military.

The patent discussed a design to provide jamming-free radio-guidance systems for submarine-launched torpedoes based on the frequency-hopping spread spectrum technique. It consisted of two identical punched paper rolls. One roll, which was located in the submarine, changed the transmission frequency as it was rotated and the other, embedded in the torpedo, aided the receiver in hopping to the appropriate frequency. By the time the enemy found the right frequency with a high-speed scanner, the frequency would have changed. As long as the hopping didn’t have a pattern that could be detected and the receiver knew the exact sequence of hopping, both snooping and jamming remained impossible.

Though ingenious, the idea was too cumbersome to implement as it involved mechanical systems and wasn’t employed by the US Navy. However, in the late 1950s, as electronic computers appeared on the scene, interest in Lamarr’s ideas was revived. A host of military applications were born in the 1960s and 1970s, followed by a boom in the 1990s for civilian applications. In fact, Lamarr’s 74-year-old patent could be considered one of the precursors of modern demands for secure personal communication systems.

Shivanand Kanavi is a former VP of TCS and adjunct faculty at NIAS. He is the author of Sand to Silicon: The Amazing Story of Digital Technology.