Physical entropy sources: SDR, thermal noise, and radio background

1. Where physical entropy comes from

Entropy measured by SDR comes from many overlapping processes: thermal fluctuations, environmental interference, receiver noise, and radio background.

It is not one ideal cosmic phenomenon, but a practical mixture of real RF-path effects.

2. Radio bands and antennas

Different radio bands produce different noise profiles. Location, antenna, channel width, and receiver electronics all affect input quality.

3. Raw signal versus random material

Raw samples should not be used directly as secure random bytes. They first require selection, quality checks, and conditioning.

4. Multiple sources instead of one

More independent nodes increase input diversity and reduce dependence on the local conditions of a single installation.

curl -s "https://entropy.sparksome.pl/sources" | jq .