original xor thing

alice.erl

-module(alice).
-export([decrypt_xor/1]).

decrypt_xor(Text) ->
	Strings = lists:map(fun(N) ->
				{N, char_distro([X bxor N || X <- Text])} end, lists:seq(0,255)),
	[{Key,_}|_] = lists:reverse(lists:keysort(2, Strings)),
	[X bxor Key || X <- Text].
	
char_distro(Text) ->
	Freqs = [
		{101, 12.5},{116, 9.3},{97, 8.0},{111, 7.6},{105, 7.5},{110, 7.2},{115, 6.5},{114, 6.3},
		{104, 5.0},{108,4.0},{100,3.8},{99,3.3},{117,2.7},{109,2.5},{102,2.4},{112,2.1},{103,1.9},
		{119,1.7},{121,1.7},{98,1.5},{118,1.0},{107,0.5},{120,0.2},{106,0.2},{113,0.1},{122,0.1},{32,5.0}
	],
	(lists:sum(lists:map(fun(N) -> case lists:keyfind(N,1,Freqs) of {N,M} -> M; _ -> 0 end end, Text))/length(Text)).