Encrypt Agent code LARP NewAge 2014

local keyUp = {
  {"A","B","C","D","E"},
  {"F","G","H","I","K"},
  {"L","M","N","O","P"},
  {"Q","R","S","T","U"},
  {"V","W","X","Y","Z"},
}
local keyLow = {
  {"a","b","c","d","e"},
  {"f","g","h","i","k"},
  {"l","m","n","o","p"},
  {"q","r","s","t","u"},
  {"v","w","x","y","z"},
}
local input = assert(io.open("normal.txt", "r"), "Failed to open input 'normal.txt' file")
local symbol, ch, text = true, nil, ""
while symbol do
  symbol = input:read(1)
  if symbol == string.char(32) then
    text = text .. " "
  elseif symbol == string.char(10) or symbol == string.char(12) then
    text = text .. string.char(10)
  elseif symbol then
    local code = nil
    for i=1,5 do
      for j=1,5 do
        if symbol == keyUp[i][j] or symbol == keyLow[i][j] then code = i .. j end
      end
    end
    if not code then code = "?" end
    text = text .. code
  end
end
print(text)
input:close()
local output = assert(io.open("encrypted.txt", "w"), "Failed to open output file")
output:write(text)
output:close()