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Comment by toddrew | Hacker News Reader

It was always visual. It seemed useless at the time, spending hours out in the pouring rain on a ship, sending a message with a flashing light to another ship, but they always reminded us that even with all our technology and cryptography, flashing light is still the most secure method of close ship-to-ship communications because it's directional when using focused light.

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Ahhh, the days before a $250 quadcopter existed to provide a plausible attack vector.

I wonder if Navy personnel are flashing base64 (base36?) encoded GPG encrypted Morse code messages to each other?

Ship to ship laser communication fixes that :) Good luck finding the beam.

Dust, mist, and/or Rayleigh scattering means I wouldn't need to be in the beampath to "see" it, but I guess if you've solved the problem of aiming a collimated laser beam from a moving ship to another moving ship, and reliably hitting the "receiver" at the far end, you can probably do it at low enough power levels to make that very hard…

Or do it with infrared.

Doesn't help - the quadcopter's cameras don't _need_ to be only sensitive to the human-visible spectrum.

(having said that, Rayleigh scattering is frequency dependant, if I recall my high school physics correctly, IR will scatter lees than visible light – I doubt thst matter though, in ship-to-ship communication there'd be more than enough mist/water in the air to scatter enough IR for a suitable camera to see the beam)

That's actually pretty great. I always loved "going back to basics", and flashing a light to talk to another naval ship is as basic as you can get. It works, it's robust in all but the worst conditions, and it's easy. Love it!

- Is he the only one looking? - Probably. - We'll have to chance that.

:) still my favorite movie

It was The Hunt for Red October, with Sean Connery.

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