Encryption Basics

Encryption transforms readable data (plaintext) into scrambled data (ciphertext) using a key — only someone with the matching key can reverse it.

Example: a very old, weak illustration of the idea

plaintext: HELLO
shift by 3
ciphertext: KHOOR

Each letter shifted 3 places forward in the alphabet: H→K, E→H, L→O, L→O, O→R. This is a Caesar cipher — genuinely ancient, and never used for real security today (it's trivially crackable), but it illustrates the core idea correctly at a tiny scale: apply a rule with a key, and reverse it with the same key.

Symmetric vs. asymmetric

Symmetric encryption uses the same key to lock and unlock — fast, but both sides need to already share that secret key somehow. Asymmetric encryption uses a public key to lock and a separate private key to unlock, which is exactly how HTTPS establishes a secure connection with a server you've never spoken to before, without needing to have shared a secret in advance.