A was a Dutch cryptographer who created a set of 6 rules for a certain kind of system. The 2nd of his set of 6 remained famous and relevant and was named after him.

B was an American mathematician, cryptographer, electrical engineer and all-round genius who, almost 100 years after A, formulated a variant of the same principle. This was in turn, named after A although they both largely mean the same! B was, of course, an incredibly prolific genius whose work, many believe, created the field of information theory and his papers are considered the most important papers of the 20th century. (consequently, B has featured on Boiledbeans many times. So this is not a dupe :P)

Another interesting (unrelated) coincidence around B was with C. B proved a certain theorem in 1949 that is fundamental to the world of information theory. Unbeknownst to B, C - who was a Swedish-born American - had pretty much proved the same thing almost 20 years before. Funnily enough, almost half-a-dozen people independently proved this over time. But, by and large, the theorem is credit to both B and C.

Identify A, B and C for 1 point. No part points. Pseudo-bonus points for naming the set of 6 rules, the maxim, and the theorem :)

Cracked by: grey_matters, username, Goyal, Sumanth Patlolla, buk, jowens, byslexia, KK, Raghuvansh, Siddarth Pai, Rogi, Thejas V R, Dibyo, shrik, Shwetha Maiya, Aditya S, badideabear, anurag, Rahulk, Bharath, Wm, rickde, Martin, amarendra, raklodramA, Ananth, Manish Achuth and Anjul