Created
July 29, 2013 12:24
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Playfair Cipher
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# Playfair Cipher | |
class PlayfairCipher | |
AZ = ('A'..'Z').to_a - ['J'] | |
def initialize keyword | |
@square = keyword.upcase.gsub(/[^A-Z]/, '').gsub('J', 'I').split('').uniq | |
AZ.each{|x| @square.push x unless @square.include? x} | |
@square = 0.step(20, 5).collect{|x| @square.slice x,5} | |
@h = AZ.collect{|x| AZ.collect{|y| "'#{x+y}' => '#{convert x, y}'"}}.flatten.join ', ' | |
@h = eval "{#{@h}}" | |
@rh = @h.invert | |
end | |
attr_reader :square | |
def convert a, b | |
ax, ay, bx, by, i = nil | |
@square.each.with_index do |line, j| | |
(ax, ay = i, j) if i = line.index(a) | |
(bx, by = i, j) if i = line.index(b) | |
end | |
case | |
when ay == by | |
@square[ay][(ax + 1) % 5] + @square[by][(bx + 1) % 5] | |
when ax == bx | |
@square[(ay + 1) % 5][ax] + @square[(by + 1) % 5][bx] | |
else | |
@square[ay][bx] + @square[by][ax] | |
end | |
end | |
def encrypt str | |
s = str.upcase.gsub(/[^A-Z]/, '').gsub('J', 'I') | |
str = '' | |
(pair, s = insert_xz(s); str << pair) while s | |
str += 'X' unless (str.length % 2).zero? | |
str.gsub(/(..)/){$1+' '}.split.collect{|s| @h[s]}.join | |
end | |
def decrypt str | |
str.gsub(/(..)/){$1+' '}.split.collect{|s| @rh[s]}.join | |
end | |
def insert_xz s | |
return [s, nil] if s.length < 2 | |
xz = @flag ? 'Z' : 'X' | |
s[0] == s[1] ? (@flag = !@flag; [s[0, 1] + xz, s[1..-1]]) : (@flag = false; [s[0, 2], s[2..-1]]) | |
end | |
end | |
#degug | |
key = "First Amendment" | |
input_message = "Ruuuuby LOOVE" | |
pc = PlayfairCipher.new key | |
p estr = pc.encrypt(input_message) | |
p pc.decrypt estr | |
require 'pp' | |
pp pc.square |
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