In 1975, Princeton physics undergraduate John Aristotle Phillips wrote a paper on how to make an atom bomb, using only publicly available information. Phillips wished to prove the technical knowledge was easily available.
If you know how, all you need to make a big bang is enriched radioactive material, which isn't easily available. The engineering base to fashion other components is available in any nation that can make a car.
Phillips designed the device and did the calculations. His adviser was the legendary Freeman Dyson, who gave him an “A” and redacted the paper from public domain.
Subsequently, North Korea
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