# Encryption

> Scrambling data so that only someone with the key can read it.

- Level: Basic
- Topics: Security
- URL: https://tidbit.legios.com.ar/encryption/
- In Spanish: [Cifrado](https://tidbit.legios.com.ar/es/encryption/)

**Encryption** turns readable data (a message, a photo, a card number) into scrambled bytes that look like noise, using a **key**. Without the key the scrambled version is useless; with it, the original comes back exactly. The recipe for scrambling is called a cipher, and the good ones, like **AES**, are public and studied by everyone. The only secret is the key.

It exists for one situation: someone else can see your bytes and you do not want them to understand them. The storage in your phone is encrypted, so a thief who pulls out the chip gets gibberish. Your messages travel encrypted, so the owner of the café Wi-Fi sees traffic but not words. HTTPS is exactly this, applied to web pages.

There are two families. **Symmetric** encryption uses the same key to lock and unlock; it is fast, so it protects the bulk of the data. Public-key cryptography uses a pair of keys and solves a different problem: agreeing on a secret with someone you have never met. Real systems combine both. Encryption also hides content, not context: who you talk to, when, and how much is usually still visible.

Practical takeaway: turn on disk encryption on your laptop (FileVault on a Mac, BitLocker or Device encryption on Windows). Phones with a lock screen already have it. And when an app says end-to-end encryption, it means not even the company can read what you send.

## An analogy

Shuffling a deck of cards following a precise sequence written on a note. Anyone can look at the shuffled deck, but only someone with the note can put it back in order.

## Keep in mind

- The algorithm is public; the key is the only secret.
- Symmetric encryption uses one key; public-key encryption uses a pair.
- It hides what you send, not usually who you send it to.
- Turn on disk encryption on your laptop; most phones already have it.

## Go deeper

- [What is encryption? (Cloudflare Learning Center)](https://www.cloudflare.com/learning/ssl/what-is-encryption/)
- [Encryption on Wikipedia](https://en.wikipedia.org/wiki/Encryption)

## Related terms

- [Chip](https://tidbit.legios.com.ar/semiconductor-chip/): A sliver of silicon carrying billions of tiny switches that compute and remember.
- [Wi-Fi](https://tidbit.legios.com.ar/wi-fi/): Networking over radio waves: the internet without the cable, within a few rooms.
- [HTTPS](https://tidbit.legios.com.ar/https/): The padlock in your browser: web traffic nobody in between can read.
- [Public-key cryptography](https://tidbit.legios.com.ar/public-key-cryptography/): Two linked keys: one you share with everyone to lock, one you keep to unlock.
- [End-to-end encryption](https://tidbit.legios.com.ar/end-to-end-encryption/): Only the sender and the recipient can read a message; the service in between cannot.
- [Algorithm](https://tidbit.legios.com.ar/algorithm/): A precise, step-by-step method for solving a problem or doing a task.