# SC 2022 Semilab: Highlights of the Cryptographic Toolbox

Cryptography, as most people know, has the answers to life's most important questions. How can we share a secret with 100 people so that any 50 of them can learn the secret if they get together, but no group of 49 of them can do so? How can I prove to you that I can tell brie from camembert without you learning anything about how I do it? How can a modern society have money without a central bank? And of course, the classic: how can we send messages over the Internet without the people who control the network being able to read our messages or concoct fake ones?

The semilab will discuss: (1) ciphers and encryption, (2) secret sharing and multiparty computation, (3) zero-knowledge proofs, and (4) cryptocurrencies and the blockchain (time permitting). Along the way we will learn some basic number theory, strategies for playing "Where's Waldo" with little kids, and other valuable life lessons.