Free online courseApplied Cryptography: AES, RSA, ECC, TLS, Tor and Bitcoin

Course Description

Modern security depends on cryptography that works reliably in real systems, not just on paper. This course helps you build applied, hands-on intuition for the algorithms and protocols that protect data every day, from messaging apps and web browsers to smart cards and cryptocurrencies. You will learn how real implementations make design trade-offs, where common failures come from, and how to reason about security properties in ways that map directly to engineering decisions.

Starting from randomness and the role of PRNGs, you will see why key reuse can instantly undermine otherwise strong schemes and how stream encryption goes wrong in practice. You will also gain the ability to recognize the importance of data encoding in security, understanding how standards such as ASN.1 and DER influence interoperability and prevent ambiguous interpretations that attackers can exploit. As you work through hashes and message authentication, you will develop a clear mental model of integrity, authenticity, and the guarantees that HMAC provides in real-world settings.

The course then connects theory to widely deployed primitives. You will strengthen your grasp of symmetric encryption with AES and learn why modes of operation matter, especially when encrypting larger or structured data. On the public-key side, you will understand how RSA and elliptic-curve cryptography enable secure key exchange and digital signatures, and why details like nonce generation in ECDSA can be the difference between strong security and catastrophic private-key leakage. You will also learn how trust is managed at scale through X.509 certificates and PKI, and how revocation mechanisms such as CRLs and OCSP fit into the lifecycle of real certificates.

Because applied cryptography lives inside systems, you will explore how signatures are packaged and time-proven in practice, as well as how smart cards protect private keys while still facing risks when endpoints are compromised. You will then dive into TLS, moving from the basic handshake to the changes that enable Perfect Forward Secrecy, gaining clarity on what the browser-server dance is actually achieving. Finally, you will see how Tor’s onion routing design limits what any single relay can learn, and how Bitcoin combines cryptographic primitives and proof-of-work to maintain a decentralized ledger. Throughout, short exercises reinforce your understanding and help you learn to spot insecure assumptions before they ship.