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.