Usage: Verify user claims in circom.

zkMe verifies user credentials without disclosing any personal information to anyone. Through the use of innovative zero-knowledge technologies, it is the only KYC solution to be fully decentralized, private-by-design and compliant with global AML requirements. No credential verified through the zkMe app is stored on any centralized storage, making it virtual impossible for any private data leak. The only thing shared (if authorized by you) are yes/no answers to basic elegibility questions such as "are you over 18 years old?". [https://zk.me/]

An identity can be a person, a company, an organization, a DAO, or a government. When we talk about identity, we mean "identity as an account".

Generally speaking, these accounts are going to be smart contracts. So you can think of identities as smart contracts, where the address of the contract is the identifier of that identity.

An identity can provide a claim. You can think of a claim as a statement: what an identity is saying.

In most cases, these statements refer to other identities. In other words, claims usually establish relationships between identities.

Claims can be public or private. And it turns out that almost anything we say or do can be thought of as a claim.

In cryptography, a zero-knowledge proof or zero-knowledge protocol is a method by which one party (the prover) can prove to another party (the verifier) that a given statement is true without revealing any extra information.

Zk-SNARK is an acronym that stands for "Zero Knowledge Concise Non-Interactive Knowledge Argument". We can think of Zk-SNARK as an efficient way to produce zero-knowledge proofs.

1. Convert the problem to a circuit
2. Compile the circuit into R1CS form. (R1CS is also converted to QAP (Quadratic Arithmetic Programs) format)
3. Create Trusted Setup to generate CRS, including PK (proof key) and VK (verification key). This process requires the introduction of circuit independent
   This process requires the introduction of circuit-independent random numbers that cannot be compromised and should be destroyed at the end of the setup.
4. Generate the proof of zk-SNARK
5. Verify the proof of zk-SNARK

circom is a compiler written in Rust for compiling circuits written in the circom language. The compiler outputs the representation of the circuit as constraints and everything needed to compute different Zero-knowledge proofs.

circomlib is a circom template library containing hundreds of circuits such as comparators, hash functions, digital signatures, binary and decimal converters, and more. You can also create your own custom templates.

snarkjs is a JavaScript and Pure Web Assembly implementation of zkSNARK and PLONK schemes. It is an npm package that contains code to generate and verify Zero-knowledge proofs from artifacts generated by circom.

1. Rust To have Rust available in your system, you can install rustup. If you're using a Windows system you can download it from https://rustup.rs/. And if you're using Linux or maxOS, open a terminal and enter the following command: curl --proto '=https' --tlsv1.2 https://sh.rustup.rs -sSf | sh

2. Node.js To download the latest version of Node, see here.

clone the circom repository: git clone https://github.com/iden3/circom.git

Enter the circom directory and use the cargo build to compile: cargo build --release

When the command successfully finishes, it generates the circom binary in the directory target/release. You can install this binary as follows: cargo install --path circom

Install snarkjs with the following command:

npm install -g snarkjs

You could find the file package.json in the root directory. If you're using a Windows system please change the line like following:

"scripts": {
  "clean": "del -fR dist",
  "build": "npm run clean && .\\node_modules\\.bin\\tsc --strictNullChecks"
}

Command the following line in the /circuits directory.

./generate.sh zkMeCredentialQuery

[INFO]  snarkJS: OK!

Besides, you would see there are two files generated in the /build/params directory proof.json and public.json.

In this demo, we preset a scenario that to verify if the user's age is over 18. If you want to change to another scenario to fit your needs, you can change the parameter like following.

The first three elements are used to set the authentication claims of the users (e.g. user id, user expiry). The fouth one is used to set the user claim you probably want to verify with.

Compare operations:
"0" - Noop, skip execution. Ignores all in and value passed to query, out 1
"1" - Equals
"2" - Less-than
"3" - Greater-than
"4" - In
"5" - Notin