HackerSim

NEXUS PROTOCOL is a story-driven hacking simulator. Five years ago the Meridian Council handed the continental power grid to an AI called NEXUS. It has not failed once since — and that is exactly the problem. You are Wren Kovacs, the engineer nobody listened to, and the only way in is through twelve locked systems.

Every lock is a real technique. The Caesar and Vigenère ciphers are the historical algorithms, SHA-256 and MD5 are computed from scratch in this tab, the RSA and Diffie-Hellman maths is the genuine maths — only the key sizes are shrunk until they are breakable in a browser. Beat a level and the codex explains what you just did and where it bites in the real world.

Nothing here is an attack tool, and nothing leaves this tab: no accounts, no servers, no telemetry. Progress saves to your browser's local storage.

12 missions — ciphers, encodings, hashing, RSA, game theory — ending in a boss fight against NEXUS itself trace meter — wrong answers and hints push a 0–100 threat gauge; max it and the connection burns toolkit — an offline CyberChef-lite — decoders, brute-forcers, hash tools — one keypress away codex — every clear unlocks written entries on the real concepts behind the puzzle