426 | 38 BANBURISmUS REVISITED
indeed the fundamental mathematical theory of the factor method. This history, which I have
seen by courtesy of GCHQ, opened with a conventional exposition of Bayes’ theorem with
traditional examples. It later exemplified its use on three ciphers which I was unaware of, as well
as its application to Banburismus and to the Japanese Naval JN25 cipher which I described in
2010.^18 As Alexander summed up:
Banburismus is about the best example of the use of scoring systems the writer has seen. It
would have been quite impossible without this technique, and the more whole-heartedly it was
employed, the better the results obtained.