Simple Login system with encryption

• Login
  • Simple login with hidden passphrase.
  • Verifies login from users.txt
• Sign Up
  • Simple sign up with hidden passphrase.
  • Checks for duplicate username under registration.
  • Saves data to users.txt
• User Encryption
  • Decrypts users.txt in start of script.
  • Encrypts users.txt in the end of the script.