BoomCrypt version 1.0

-- BoomCrypt - the simple file encryptor
-- Not to be confused with bcrypt, the secure hashing function
-- Written by MasterOfBooms/BoomBoomLHack
-- version 1.0
-- Credits to SquidDev, ElvishJerricco, KillaVanilla, and Anavrins for their APIs

local version = "1.0"
os.loadAPI("sha")
os.loadAPI("b64")
os.loadAPI("aes")
os.loadAPI("rng")
os.loadAPI("json")

local args = {...}
local tFile = args[2]
local passBullet = string.char(7)
local function PRNG()
 local r = 0
 for i=1,math.random(128,512) do
  local g = math.random(32768)
  local s = math.random(4096)
  r=r+g
  r=r-s
 end
 return r
end

local function initCSPRNG()
 rng.initalize_mt_generator(PRNG())
 rng.seed_from_mt(PRNG())
 rng.generate_isaac()
end
local function genIV()
 local iv = {}
 initCSPRNG()
 for i=1,16 do
  iv[i] = rng.random(1,255)
 end
 return iv
end
local function genKey(i)
 local s = sha.digest(i)
 local p = sha.pbkdf2(i,s,1024)
 return p:toHex()
end
local function byteToStr(bs)
 local str = ""
 for i=1,#bs do
  local cha = string.char(bs[i])
  str = str..cha
 end
 return str
end
local function strToByte(str)
 local bs = {}
 for i=1,str:len() do
  local cha = string.byte(str:sub(i,i))
  table.insert(bs,cha)
 end
 return bs
end
local function encrypt(pwd,msg)
 local key = genKey(pwd)
 local iv = genIV()
 local cr = aes.encrypt(key,msg,aes.AES256,aes.CTRMODE,iv)
 local bs = strToByte(cr)
 local out = b64.encode(bs)
 return out,iv
end
local function decrypt(pwd,msg,iv)
 local key = genKey(pwd)
 local bs = b64.decode(msg)
 local ci = byteToStr(bs)
 local out = aes.decrypt(key,ci,aes.AES256,aes.CTRMODE,iv)
 return out
end
local function printUsage()
 local progName = shell.getRunningProgram()
 print("Usage:")
 print(progName.." <encrypt/decrypt> <file>")
end
local function fileOper(oper,file,data)
 if oper == "r" then
  local file = fs.open(file,"r")
  local out = file.readAll()
  file.close()
  return out

 elseif oper == "w" then
  local file = fs.open(file,"w")
  file.write(data)
  file.close()
 elseif oper == "d" then
  fs.delete(file)
 elseif oper == "e" then
  return fs.exists(file)
 end
end

print("BoomCrypt version "..version)
if #args < 2 then
 printError("Not enough arguments!")
 printUsage()
 return
end
if args[1] == "encrypt" then
 if fileOper("e",tFile) then
  write("Password: ")
  local key = read(passBullet)
  write("Encrypting, please wait... ")
  local rf = fileOper("r",tFile)
  local fb = b64.encode(strToByte(rf))
  local cry,iv = encrypt(key,fb)
  local data = {}
  data["boomCrypt"] = version
  data["cryptData"] = cry
  data["IV"] = iv
  data["cryptChecksum"] = sha.digest(cry):toHex()
  data["orginChecksum"] = sha.digest(fb):toHex()
  local out = json.encode(data)
  fileOper("d",tFile)
  fileOper("w",tFile,out)
  print("success!")
 else
  printError("File not found!")
  return
 end
elseif args[1] == "decrypt" then
 if fileOper("e",tFile) then
  local data = json.decode(fileOper("r",tFile))
  if not data then
   printError("Invaild or corrupted BoomCrypt file!")
   return
  elseif not data["boomCrypt"] == version then
   printError("BoomCrypt file version mismatch")
   print("This BoomCrypt file is not compatible with this version of BoomCrypt.")
   return
  end
  if data["boomCrypt"] then
   write("Password: ")
   local key = read(passBullet)
   write("Decrypting, please wait... ")
   local rf = fileOper("r",tFile)
   local data = json.decode(rf)
   local fb = data["cryptData"]
   local iv = data["IV"]
   local cs = data["cryptChecksum"]
   local gs = data["orginChecksum"]
   local cryChk = sha.digest(fb):toHex()
   if not cryChk == cs then
    print("failed.")
    printError("Checksum mismatch: Encrypted data")
    return
   end
   local dey = decrypt(key,fb,iv)
   if not dey then
     print("failed.")
     printError("Invaild password!")
     return
   end
   local orgChk = sha.digest(dey):toHex()
   if not orgChk == gs then
    print("failed.")
    printError("Checksum mismatch: Decoded data")
    return
   end
   local out = byteToStr(b64.decode(dey))
   fileOper("d",tFile)
   fileOper("w",tFile,out)
   print("success!")
  else
   printError("Invaild or corrupted BoomCrypt file!")
   return
  end
 else
  printError("File not found!")
 end
else
 printError("Unrecognized subcommand!")
 printUsage()
 return
end