RNG White Noise Tests



For the upcoming White Noise Boutique, I’ll be generating bespoke white noise for visitors using a variety of methods. These quick tests show that, while they sound essentially the same, different algorithms do in fact generate different white noise. For each generator, a spectrogram and frequency plot are shown for a ten-second sample. The plots were generated with Audacity.

Above: the AES_OFB algorithm from the Dieharder suite, one of two cryptographically-secure methods.



Linear congruential generator, an old-fashioned and non-secure generator.



The only “true” generator here, via the operating system’s built-in “dev/random” command, which creates random numbers from hard drive entropy.



The Threefish generator, also via the Dieharder suite and the other cryptographically-secure algorithm.

Racal MA-4204 Time Division Voice Scrambler


Another device using random acoustic noise for cryptographic purposes. This device from the early 1970s randomly rearranges the audio signal every half-second; a corresponding unit puts the audio back in the correct order on the other end. While not very secure (the three 8-position switches only provide 512 possible combinations), this device’s operation and style have a nice mix of of functionality and poetics.

Via Cryptography Museum.