After this lesson, you will be able to: Understand the three goals cryptography provides (confidentiality, integrity, authenticity) and the three families of primitives that deliver them.
Cryptography is the math underneath every secure system: HTTPS, password storage, signed software, messaging apps. This subtrack takes you from zero to being able to choose and use the right primitive correctly. It covers symmetric and asymmetric encryption, hashing and HMAC, key exchange and signatures, TLS 1.3, and practical guidance on which library to use and what never to build yourself.
This is a free introductory lesson. No purchase required.
Three goals. Confidentiality: only the intended party can read the data (encryption). Integrity: tampering is detectable (hashes, MACs). Authenticity: you know who you are talking to (signatures, certificates). Most real systems need all three at once. HTTPS, for example, encrypts (confidentiality), checks message integrity, and authenticates the server with a certificate.
Symmetric encryption: one shared key encrypts and decrypts; fast, used for bulk data (AES). Asymmetric encryption: a public/private key pair; slower, used to exchange keys and to sign (RSA, ECC). Hash functions: one-way fingerprints of data; used for integrity, passwords, and signatures (SHA-256). Real protocols combine them: asymmetric crypto bootstraps a shared symmetric key, then symmetric crypto does the heavy lifting.