[RAW] Registration and Authorization

Sorry for my bad english, cause it's not my main language.

I'm noob in a CC, don't be rude with me :)/>
What can I add to protect\upgrade my system of Reg\Auth?
Code:

--APIs
os.pullEvent = os.pullEventRaw
os.loadAPI("/DZSystem/API/Color")

--Variables
local quit, user, registered = false
local name, pass, passCnfrm = nil
local usersDir = "/DZSystem/users/"
local regStr = "Registration"
local authStr = "Authorization"
local program = "V 1.0"

--Functions
local function clr(color,str)
  term.setBackgroundColor(color)
  term.setCursorPos(1,1)
  term.clear()
  print(str)
  for i=1,50 do
	if i == 50 then
	  print("-")
	else
	  write("-")
	end
  end
end

repeat
clr(Color.Lime,program)
print("Do you have account?")
print("Y\N")
local event, key = os.pullEvent()
until (key == keys.y) or (key == keys.n)
if key == keys.y then
--Begin Registration
  repeat --begin
	clr(Color.Lime,regStr)
	write("Enter your name: ")
	name = read()
	user = fs.exists(usersDir..name)
	if user == true then
	  clr(Color.Lime,regStr)
	  print("User already registered!")
	  print("Try another name.")
	  sleep(1)
	else
	  quit = true
	end
  until quit == true --end
	quit = false
	print("Ok!")
	sleep(1)
	quit = true
  repeat --begin
	clr(Color.Lime,regStr)
	write("Enter your password: ")
	pass = read("*")
	write("Confirm your password: ")
	passCnfrm = read("*")
	if pass == passCnfrm then
	  print("Ok!")
	  sleep(1)
	  quit = true
	else
	  quit = false
	  clr(Color.Lime,regStr)
	  print("Incorrect password!")
	  sleep(1)
	end
  until quit == true --end
  file = fs.open(usersDir..name,"a")
  --file.writeLine(name)
  file.writeLine(pass)
  file.close()
  sleep(2)
--End Registration
else
--Begin Authorization
  quit = false

  repeat --begin
	clr(Color.Lime,authStr)
	write("Enter your name: ")
	name = read()
	user = fs.exists(usersDir..name)
	if user == true then
	  print("Ok!")
	  file = fs.open(usersDir..name,"r")
	  passCnfrm = file.readLine()
	  file.close()
	  sleep(1)
	  quit = true
	else
	  clr(Color.Lime,authStr)
	  print("User is not exists! Try again.")
	  sleep(1)
	end
  until quit == true --end
  quit = false
  repeat
	clr(Color.Lime,authStr)
	write("Enter your password: ")
	pass = read()
	if pass == passCnfrm then
	  print("Ok!")
	  sleep(3)
	  quit = true
	else
	  clr(Color.Lime,authStr)
	  print("Incorrect password!")
	  sleep(1)
	end
  until quit == true
end