This feels like something that’s a neat claim and will work against simple setups, but less accurate for more complicated scenarios (eg Tor). Then you’re really just relying on how accurate your knowledge of the proxies are.

Also, the readme has slightly incorrect logic I think:

> According to Special Relativity, information cannot travel faster than the speed of light. Therefore, if the round trip time (RTT) is 4ms, it's physically impossible for them to be farther than 2 light milliseconds away, which is approximately 600 kilometers.

It calls out the 33% for fiber but ignores that there’s not a straightline path between two points on the network and there could be wireless, cable, and DSL links somewhere on that hop.

Also, the controlled variable here is latency, not distance. Thus you can always increase latency through buffering and therefor you could be made to appear further than you are. And that buffering need not even be intentional - your perceived distance estimate will vary based upon queuing delays in intermediary depending on time of day (itself a fingerprint if you incorporate time-aware measurements, but a source of error if you don’t).

Fingerprinting is hard and I dislike the framing that it’s absolutely impossible to mask or that there’s not false positive and false negative error rates with the fingerprint.