Cheap entropy using RTL-SDR dongle

We’ve seen the RTL-SDR dongle used for a number of interesting projects, but here’s an unusual one not directly related to signal monitoring. Noel Bourke was considering the topic of entropy and randomness as it relates to encryption and came up with a unique use for the RTL-SDR.

When RTL-SDRs came on the market back in 2012 my first thought was “Oooh! a cheap homemade radio noise RNG!”. RTL-SDRs are USB TV tuners based on the RTL2832U chipset. Rather than building a different tuner for each market’s frequencies, Realtek built a cheap wide-band software defined radio, wrote the TV tuner in software and then built millions of units for less $1 a piece. So we can just turn the RTL-SDR on, sample everything it can see and instead of a TV tuner we have an ultra wide-band radio entropy source! Before reinventing the wheel I did a quick search and found Paul Warren’s RTL-Entropy.

So today I was installing ArchLinux on one of my computers and decided it would be probably be a good idea to document a few things I usually do. And if I do that, I might as well just stick my documentation on a blog in the hope it’s useful to someone else.

You can find Noel’s post on SecurityLaxity.

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