Scytale Encryption

-- pronounced ski-tah-lee just fyi

function switchConvert(num)
  if num >= 0 and num < 10 then
    return num
  elseif num == 9 then
    return 'a'
  elseif num == 10 then
    return 'b'
  elseif num == 11 then
    return 'c'
  elseif num == 12 then
    return 'd'
  elseif num == 13 then
    return 'e'
  elseif num == 14 then
    return 'f'
  elseif num == 15 then
    return 'g'
  elseif num == 16 then
    return 'h'
  elseif num == 17 then
    return 'i'
  elseif num == 18 then
    return 'j'
  elseif num == 19 then
    return 'k'
  elseif num == 20 then
    return 'l'
  elseif num == 21 then
    return 'm'
  elseif num == 22 then
    return 'n'
  elseif num == 23 then
    return 'o'
  elseif num == 24 then
    return 'p'
  elseif num == 25 then
    return 'q'
  elseif num == 26 then
    return 'r'
  elseif num == 27 then
    return 's'
  elseif num == 28 then
    return 't'
  elseif num == 29 then
    return 'u'
  elseif num == 30 then
    return 'v'
  elseif num == 31 then
    return 'w'
  elseif num == 32 then
    return 'x'
  elseif num == 33 then
    return 'y'
  elseif num == 34 then
    return 'z'
  else
    return "-"
  end
end

function fill()
  local initial = math.random(34)

  local parsedInitial = switchConvert(initial)

  return parsedInitial
end

function wrap(parchment, sec)
  local point = 1
  local wrap = ""
  local stick = ""
  local parchLen = #parchment

  for point=1,parchLen do
    local nextLen = math.random(sec)
    stick = stick..nextLen

    for i=1, nextLen - 1 do
      wrap = wrap..scytale.fill()
    end

    wrap = wrap..string.sub(parchment, point, point)
  end

  return wrap, stick
end

function unwrap(parchment, stick)
  local unwrap = ""
  local wrappedLen = #parchment
  local point = 0
  local stickPoint = 1

  while true do
    stickCurrent = string.sub(stick, stickPoint, stickPoint)

    if point == wrappedLen then
      break
    end

    point = point + stickCurrent
    stickPoint = stickPoint + 1

    unwrap = unwrap..string.sub(parchment, point, point)
  end

  return unwrap
end