Cryptology Academy · Lesson

Crypto in Everyday Life

See how cryptography protects your messages, passwords, and payments today.

Lesson 4 of 413 steps

Crypto in Everyday Life is a free Cryptology Academy lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Cryptology Academy learning path, and your progress syncs across the web and the CoddyKit app. The Cryptology Academy course includes 4 lessons in total.

Welcome

Cryptography protects nearly every digital interaction you have. In this lesson we map real-world technologies to the crypto primitives underneath them.

HTTPS & TLS

When your browser shows a padlock, TLS is running. It uses certificate validation, ECDH key exchange, AES-GCM encryption, and HMAC authentication together.

WhatsApp End-to-End Encryption

WhatsApp uses the Signal Protocol: X3DH key agreement and Double Ratchet for forward-secret message encryption. Your messages are encrypted on your device.

Password Storage

Good services never store your password — they store bcrypt(password + salt). Even if their database is leaked, your password stays safe.

Bitcoin & Crypto Wallets

Bitcoin addresses are derived from ECDSA public keys on secp256k1. Sending coins requires signing a transaction with your private key — lose it, lose the coins.

SSH Key Authentication

SSH uses public-key authentication: the server encrypts a challenge with your public key; your client decrypts it with the private key to prove identity.

Code Signing

App stores and OS updates are code-signed: the developer hashes the binary and signs the hash with their private key. Your OS verifies before installing.

Two-Factor Authentication (TOTP)

TOTP (Google Authenticator) uses HMAC-SHA1 over a timestamp and shared secret. Both the server and your device compute the same 6-digit code each 30 seconds.

VPN & WireGuard

WireGuard uses Curve25519 ECDH, ChaCha20-Poly1305 AEAD, and BLAKE2 MACs. It achieves better security than IPSec with far fewer lines of code.

Email Encryption: PGP & S/MIME

PGP encrypts email with the recipient's RSA or ECC public key and signs with the sender's private key, providing both confidentiality and authentication.

Disk Encryption

BitLocker (Windows) and FileVault (macOS) use AES-XTS to encrypt your entire disk. The key is wrapped with your password via PBKDF2 or Argon2.

Quick Check

Which cryptographic primitive does TOTP (Google Authenticator) use to generate one-time codes?

Answer it in the interactive lesson

Recap

Amazing! Cryptography is everywhere. You've seen it in HTTPS, messaging, passwords, wallets, and more. The rest of this course builds each primitive from scratch.

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Write and run real code in your browser, get instant help from a 24/7 AI tutor, and pick up where you left off on the web or in the app.

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Lessons: 261

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Frequently Asked Questions

Is the “Crypto in Everyday Life” lesson free?

Yes — the full text of “Crypto in Everyday Life” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Cryptology Academy course, upgrade to CoddyKit PRO. The Cryptology Academy course includes 4 lessons in total.

What will I learn in “Crypto in Everyday Life”?

See how cryptography protects your messages, passwords, and payments today. You practise Cryptology Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Cryptology Academy?

No prior experience is required. Cryptology Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.

How long does the “Crypto in Everyday Life” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Cryptology Academy lesson?

Yes. Every Cryptology Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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