This document provides a conceptual introduction to cryptographic methods. It explains that cryptography works by using the XOR operator and one-time pads or stream ciphers to encrypt messages. With one-time pads, a message is XOR'd with random data and can only be decrypted by someone with the pad. Stream ciphers generate pseudo-random streams from a key and nonce to encrypt messages. Public-key encryption uses Diffie-Hellman key exchange to allow parties to establish a shared secret to encrypt messages.