Hashing: fingerprints of data

Welcome to Cryptography Foundations — the first pillar of the Security discipline. Before any protocol can protect a connection or prove an identity, it leans on a handful of primitives. This pillar builds those primitives as small, understandable toys so the protocols later in the discipline stop being magic.

Every module here follows one thread: concept → protocol → attack → defence. You meet the idea, see how the mechanism works, look at the canonical way it breaks, and build the defence — the graded exercise is always the defence, never the attack.

We start with the cryptographic hash: a fixed-size fingerprint of any input, the workhorse of integrity. This ladder builds a content fingerprint, then the right way to store a password on top of it.

The code runs entirely in your browser (Pyodide — Python compiled to WebAssembly); nothing leaves your machine. Run checks the visible tests; Submit grades against hidden tests; the reference solution unlocks once you pass.