Cryptography is what keeps passwords, messages and web traffic private, and it is also where many real-world security mistakes are made. This module explains the building blocks so you can choose them correctly. You'll start with hashing: what it does, why it is one-way, and why passwords need a salt to resist rainbow table attacks.
Then you'll compare symmetric encryption (one shared key, fast) with asymmetric encryption (a public and private key pair), and see how digital signatures provide authentication, integrity and non-repudiation. From there you'll look at certificates, certificate authorities and the chain of trust behind PKI, and finish by following a TLS handshake to see how all of these pieces secure an HTTPS connection.
With the cryptography in place, you'll be ready for the next module, Network Security, where you defend the networks that carry this traffic.
What hashing is, why identical passwords produce identical hashes, how a salt fixes that, and how salting defeats precomputed rainbow tables.
One shared key versus a public and private key pair, why symmetric encryption is fast, and the trade-offs between speed and security.
How hash-then-sign works and what digital signatures guarantee: authentication, integrity and non-repudiation, with uses in TLS certificates and code signing.
Why HTTPS needs certificates, how a server proves its identity, what certificate authorities do, and how a certificate is verified.
How a client and server agree to start talking in code: the TLS handshake step by step, explained by Dr Mike Pound.