# ZK Frontiers: Week 3 Exercises For this week's exercise, you will write a spec for one of the following proposed applications. If you are working on a project, you're automatically "exempt," as you'll already be building one of these! In your spec, you should: - Outline precisely the ZK circuit(s) you'll be using. You can use [our template from class](https://docs.google.com/presentation/d/1MFbU1gOB228Kn7LkwxuqWt6BwCcrIGILRKb7yRMwtoQ/edit#slide=id.g24f2a51b284_0_806) if you'd like. - Describe the business logic of the major components of the application: the server (what it stores, what it verifies, etc.) smart contracts (if applicable), clients (what they store, what they prove, etc.), and any additional services (for example, an auxiliary server that stores, verifies, and serves Merkle groups). ## WhaleChat Build an anonymous message board, without persistent identities, that only ETH whales--anyone with knowledge of a private key corresponding to an Ethereum account with at least 1000 ETH as of the time of posting--can post to. ### Extension: Integrate into Zupass and Zuca.st Add an "ETH Whale badge" feature to Zuca.st. Anyone who is an ETH Whale can add a "Whale" badge to their profile, which would be displayed alongside all of their messages. The flow might look something like: - Add an [eth-pcd](https://eth-pcd.vercel.app/) your Zupass, for an account you control with at least 1000 ETH. - Add a button to zuca.st that requests a proof that you hold a Semaphore keypair and a linked ETH PCD in your Zupass, such that the ETH account is in a Merkle tree of accounts with at least 1000 ETH. - On verification of this proof, the zuca.st server will display a badge alongside your user ID in future posts. ## ZK Battleship Design a peer-to-peer simplified Battleship game where the two players can't lie about the position of their ships, once they've committed to their positions. (To simplify this, you can also imagine that you're building this in a traditional client-server architecture, but the server just serves as an untrusted store of data). - Both players should initially commit to a 5 by 5 board with two ships: a ship of length 2 (i.e. a contiguous 2x1 or 1x2 rectangle), and a ship of length 3 (i.e. a contiguous 3x1 or 1x3 rectangle). - Players take turns, alternating making coordinate pair guesses. - Each time your opponent makes a guess, you must respond with a proof that their guess did or did not hit one of your ships. - The first player to sink both of their opponent's ships wins. ## ZK Twitter Import Build an anonymous message board, without persistent identities, that only Twitter influencers--anyone with at least 100,000 Twitter followers--can post to. ### Extension: Integrate into Zupass and Zuca.st Add a "Twitterati badge" feature to Zuca.st. Anyone who is has a Twitter following of at least 100K can add a "Twitterati" badge to their profile, which would be displayed alongside all of their messages. The flow might look something like: - Add an RSA-signed Twitter password reset email your Zupass. - Add a button to zuca.st that requests a proof that you hold a specific Semaphore keypair, and that you have a password reset email signed by Twitter, such that the account in that email is in a pre-generated Merkle tree of Twitter handles with at least 100K followers. - On verification of this proof, the zuca.st server will display a badge alongside your user ID in future posts. ## ZK NFTs This project idea is to build a system of NFTs with default private ownership. They do not need to be ERC721-compliant. zkNFTs come in two types: - shielded: ownership is not known. Instead, a commitment is stored on-chain that is the hash of a "UTXOs": `ownerAddress | nftID | salt` - unshielded: ownership is known. Define the state variables of a hypothetical ZK NFT contract, as well as pseudocode for how each of the following functions would work: `mint(id, address)`: - purpose: mints an unshielded NFT with public ID `id` and public owner `address` `shield(address, id, utxoHash, proof)`: - purpose: turns an unshielded NFT into a shielded NFT `unshield(address, id, salt, merkleIdx)`: - purpose: reveals that `address` owns NFT with id `id`, turning it into an unshielded NFT `transferShielded(nullifier, newUtxoHash, proof)`: - purpose: transfers ownership of a shielded NFT `transferUnshielded(nullifier, newUtxoHash, proof)`: - purpose: transfers ownership of a shielded NFT
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ZK Frontiers: Week 2 Exercises

ZK Passwords In this exercise, you will implement a ZK-based password verifier! Instructions can be found in the README of the scaffolding repo. You are aiming to produce something that looks like this video demo. You can start with the scaffolding repo, or you can roll your own from scratch. If you use the scaffold repo, make sure to check out circom-starter, the base repo which this is based on! Extension: make proving happen in-browser. We’ll go over this during next week’s Monday optional session. You may also find this circom and snarkjs diagram useful.

6/6/2023
ZK Frontiers: Week 1 Exercises

This week's exercises are hands-on coding exercises. Try writing the following circuits on your own. If you get stuck, you can check the solutions. We'll go over these circuits in the second Optional Session in Week 2. If you need to look up circom language features or syntax, take a look at the circom docs. I recommend trying to build these circuits in zkREPL, for fast iteration. I recommend doing these exercises in order, as later circuits may build on previous ones. References Field Size All signals in circom are treated as numbers modulo this big prime:

6/1/2023
Zupass Resources for Developers

Zupass Official Repo: https://github.com/proofcarryingdata/zupass The README provides a starting point for devs. Usage Examples for Devs: https://consumer-client.onrender.com This page contains examples for devs on how to integrate Zupass into various application flows, such as authentication, proof generation/consumption. Code for these examples is in the official Zupass repo. Example Application: Zuzalu Confessions: https://confessions-client.onrender.com/ This is a fully-functional anonymous message board built on Zupass, demonstrating authentication and identity-hiding proofs. For development/demonstration/reference purposes only! Zuzalu Confessions Reference Code: https://github.com/proofcarryingdata/zuzalu-confessions

4/11/2023
Syncing Your Zuzalu Passport

The Zuzalu Passport is an app that lets you prove that you are a Zuzalu resident or visitor (using zero-knowledge cryptography!). You'll use it to access both digital and physical spaces at Zuzalu. For example, your Passport will generate a QR code that you can show on mobile, that can be scanned for access to Zuzalu co-working spaces. Your Passport also allows you to log into the Zuzalu website, to sign up for Zuzalu events. Once you've created your Passport, if you want to use your Passport on a device other than the one you first logged in on, you'll need to follow two easy steps. Step 1: Copy your Passport Key from your original device To do this, hit the settings icon in the top right-corner of the Passport app, and then tap "Copy Key for Sync."

4/7/2023
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