1. Why an SDR makes a good entropy source
A software-defined radio digitizes whatever the antenna picks up: cosmic background radiation, atmospheric noise, and the receiver's own thermal and quantum noise. Tuned to a quiet patch of spectrum with no strong broadcast signal, that output is dominated by physical noise rather than any predictable transmission.
Because SDR hardware is cheap, widely available (RTL-SDR dongles cost a few dollars), and produces a continuous digital sample stream out of the box, it's a practical way to build a hardware entropy source without custom electronics.
2. From I/Q samples to random bits
Galactropy's SDR nodes read the receiver's I/Q (in-phase/quadrature) sample stream and extract the least-significant bits of the analog-to-digital converter output: the part of the signal dominated by noise floor rather than any tuned-in signal. Those bits are streamed to the central generator over the local network.
3. Multiple nodes, one pool
The architecture supports any number of SDR nodes running in parallel, each contributing samples to the same shared entropy pool; a node dropping offline just reduces throughput, it doesn't take the service down. Node health and per-source audit scores are published live.
View current statistical reports ->4. Getting random numbers out
The pool is exposed over HTTP and TCP, plus ready-made endpoints for common formats: raw bytes, hex, base64, UUIDs, and tokens:
curl -s "https://galactropy.com/v1/random/uuid"