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Comment by runeb | Hacker News Reader

Could you attack WWVB receivers by overriding the transmitted signal and change their time?

edit: Not something I'd want to do obviously, just seems like a rather insecure technology.

I believe you can if your signal is strong enough relative to the real one, which can be pretty weak in certain areas (hence the need for this device).

My high school's math and science club tried to do this once to the school's clocks as a prank. We never got the transmission circuitry working, but I did write a program for my graphing calculator that computed and outputed the correct signal sequence for a given timestamp through its 2.5mm jack.

Edit to add: As I recall, our particular clocks synced at midnight or if you hit the reset button. I think that was to increase the chances of a good signal.

What calculator was that? That sounds like a lot of fun!

Mine was a TI-84, although an 83 would have worked too. I wrote it in native assembly, since TI-BASIC doesn'the give you enough control. You can do clever things with that jack, like play music if you've got a 2.5-to-3.5mm adapter.

And yeah, it was a blast!

How did you get programs to and from the calculator? Did you type it all out by hand on the calculator?

There's a USB adapter and software that lets you transfer files/scripts to and from the calculator. You can also record data over that port as well.

I developed programs on my computer and transferred them. There's some fantastic communities out there with all the resources and help you'll ever need [1]. I got my start working through this guide [2].

[1] https://www.omnimaga.org

[2] http://tutorials.eeems.ca/ASMin28Days/welcome.html

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