One-Time Pad

The only theoretically unbreakable cipher. It uses a random key that is as long as the message and is used only once.

How it works:

  • Key must be truly random and as long as the message
  • Each character is XORed with the corresponding key character
  • The key must never be reused (hence "one-time")
  • Mathematically proven to be unbreakable when used correctly