Clifford Cocks
lorecryptography
The GCHQ mathematician who in 1973 worked out an implementation of Ellis's idea - equivalent in substance to what became RSA - four years before RSA was published.
He is reported to have done it in an afternoon and then filed it, because there was nothing else to do with it. The work stayed secret until the late 1990s, so it influenced nothing: no standard cites it, no library implements it, and the industry that grew up around the same mathematics grew up entirely on the published version. The episode is the cleanest available answer to whether secrecy or publication produces more capability, and it is not close.
Also known as: cocks