ComputerCraft Encryption - crypto API

-- crypto API
-- Encryption software for ComputerCraft
-- Enjoy! -computer
---------------------------------------------------
--  Global Variables:

local charList =  {"A", "B", "C", "D", "E", "F",
		"G", "H", "I", "J", "K", "L", "M", "N", "O",
		"P", "Q", "R", "S", "T", "U", "V", "W", "X",
		"Y", "Z", "a", "b", "c", "d", "e", "f", "g",
		"h", "i", "j", "k", "l", "m", "n", "o", "p",
		"q", "r", "s", "t", "u", "v", "w", "x", "y",
		"z", " ", ".", ",", "!", "?", "'", "-", "_",
		"1", "2", "3", "4", "5", "6", "7", "8", "9",
		"0", "@", "#", "$", "%", "^", "&", "*", "=",
		"+", "-", "/", "(", ")", "[", "]", "{", "}",
		"<", ">", "\"", "'", ":", ";", "&frac12;", "&frac14;",
		"¡", "¿", "~", "⌂", "Ç", "ü", "é", "â", "ä",
		"à", "å", "Ç", "ê", "ë", "è", "ï", "î", "ì",
		"ä", "å", "é", "æ", "æ", "ô", "ö", "ò", "û",
		"ù", "ÿ", "ö", "ü", "£", "ñ"}

local reverseCharList = {}
for i = 1, #charList do
  reverseCharList[charList[i]] = i
end

---------------------------------------------------
-- Functions:

-- crypto.toBinary(text)
-- crypto.fromBinary(binary)
-- crypto.genSequence(key, length)
-- crypto.applyShift(text, key)

function toBinary (text)
  local binary = {}

  for i = 1, #text do
	local num = reverseCharList[text:sub(i, i)] - 1
	local curBit = 64

	for j = 1, 7 do
	  if bit.band(curBit, num) == curBit then
		binary[#binary + 1] = "1"
	  else
		binary[#binary + 1] = "0"
	  end

	  curBit = curBit / 2
	end
  end

  return table.concat(binary)
end

function fromBinary (binary)
  local text = {}

  for i = 0, #binary / 7 - 1 do
	local num = 0
	local curBit = 64

	for j = 0, 6 do
	  local stringPos = i * 7 + j + 1

	  if binary:sub(stringPos, stringPos) == "1" then
		num = num + curBit
	  end

	  curBit = curBit / 2
	end

	text[i + 1] = charList[num + 1]
  end

  return table.concat(text)
end

function genSequence (key, length)
  local sequence = {}
  local num = key

  while #sequence < length do
	local curBit = 64

	num = num ^ 2 + 1
	if string.len(tostring(num)) > 3 then
	  num = math.floor(num / 100)
	end
	while num > 127 do
	  num = num - 127
	end

	for j = 0, 6 do
	  if bit.band(curBit, num) == curBit then
		sequence[#sequence + 1] = "1"
	  else
		sequence[#sequence + 1] = "0"
	  end

	  curBit = curBit / 2
	end
  end

  return table.concat(sequence)
end

function applyShift (text, key)
  local binText = toBinary(text)
  local binOutput = {}

  for i = 1, #binText do
	local seq = genSequence(key, #binText)
	local digit

	if binText:sub(i, i) == seq:sub(i, i) then
	  digit = 0
	else
	  digit = 1
	end

	binOutput[i] = digit

	key = key + 1
  end

  return fromBinary(table.concat(binOutput))
end