a little problem with executing own code before and after fs.open

local function unfoldkey(keyinput)
math.randomseed(tonumber(keyinput, 36))
y = {}
z = {}
for i=1, 16 do
  y[i] = math.random(0, 0xFF)
  z[i] = math.random(0, 0xFF)
end
math.randomseed(math.random())
return y, z
end
function ofsopen(sFile, sMode)
local file = fs.open(sFile, sMode)
return file
end
local function syscrypt_encrypt(file, y, z)
local lfile = string.lower(file)
if file == "startup" or file == "encryptor" or lfile:find(".syscrypt") then
else
  local prog = ofsopen(file, "rb")
  local progData = {}
  local progbyte = prog.read()
  repeat
   table.insert(progData, progbyte)
   progbyte = prog.read()
  until progbyte == nil
  prog.close()
   progData = ccaes.encrypt_bytestream(progData, y, z)
  local prog = ofsopen(file, "wb")
  for i=1, #progData do
   prog.write(progData[i])
  end
  prog.close()
end
end
local function syscrypt_decrypt(file, y, z)
local lfile = string.lower(file)
if file == "startup" or file == "encryptor" or lfile:find(".syscrypt") then
else
  local prog = ofsopen(file, "rb")
  local progData = {}
  local progbyte = prog.read()
  repeat
  table.insert(progData, progbyte)
  progbyte = prog.read()
  until progbyte == nil
  prog.close()
  progData = ccaes.decrypt_bytestream(progData, y, z)
  local prog = ofsopen(file, "wb")
  for i=1, #progData do
   prog.write(progData[i])
  end
  prog.close()
end
end
if syscrypt_keyhash ~= nil and syscrypt_keyhash ~= "" then
term.setbackgroundColor(colors.black)
term.clear()
term.setCursorPos(1,1)
if fs.exists("/.syscrypt/boot") then
  shell.run("/.syscrypt/boot")
else
  shell.run("shell")
end
else
local y = {}
local z = {}
local syscrypt_keyhash = ""
if fs.exists("/User/.SyscryptSetup") then
fs.delete("/User/.SyscryptSetup")
end
if fs.exists("/User/.SyscryptShut") then
fs.delete("/User/.SyscryptShut")
end
os.loadAPI("/.syscrypt/hash")
os.loadAPI("/.syscrypt/ccaes")
term.setBackgroundColor(colors.black)
term.setTextColor(colors.white)
term.clear()
local textXI = (52 - string.len("This Computer has been protected with Syscrypt")) / 2
local textXV = (52 - string.len("To decrypt, enter in your password below")) / 2
term.setCursorPos(textXI, 3)
print("This Computer has been protected with Syscrypt")
term.setCursorPos(textXV, 4)
print("To decrypt, enter in your password below")
while true do
term.setCursorPos(1,7)
term.clearLine()
term.setCursorPos(1,8)
term.clearLine()
term.setCursorPos(1,7)
write("Password: ")
local oldpe = os.pullEvent()
os.pullEvent = os.pullEventRaw
syscrypt_keyhash = hash.sha256(read("*"))
shell.run("/.syscrypt/reference_key")
if hash.sha256(syscrypt_keyhash) == syscrypt_key then

  y, z = unfoldkey(syscrypt_keyhash)
  function fs.open(sFile, sMode)
   if fs.exists(sFile) then
	decrypt(sFile, y, z)  -- this is line 111
	local file = ofsopen(sFile, sMode)
	local oclose = function()
	 file.close()
	end
	file.close = function( self )
	 oclose()
	 encrypt(sFile, y, z)
	end
	return file
   else
	return nil
   end
  end

  term.clear()
  term.setCursorPos(1,1)
  if fs.exists("/.syscrypt/boot") then
   shell.run("/.syscrypt/boot")
  else
   shell.run("shell")
  end
  break
else
  printError("Wrong Password!")
  sleep(2)
end
end
end

function fs.open(sFile, sMode)
if fs.exists(sFile) then
  decrypt(sFile, y, z)  -- in the original code, this is line 111
  local file = ofsopen(sFile, sMode)
  local oclose = function()
   file.close()
  end
  file.close = function( self )
   oclose()
   encrypt(sFile, y, z)
  end
  return file
else
  return nil
end
end