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113 lines
3.4 KiB
Markdown
113 lines
3.4 KiB
Markdown
# javascript implementation of zkSnark
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This is a javascript implementation of zkSnarks.
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This library allows to do the trusted setup, generate proofs and verify the proofs.
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This library uses the compiled circuits generated by the jaz compiler.
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## Install
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```
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npm install zkSnark
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```
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## Usage
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### import
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```
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const zkSnark = require("zksnark");
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```
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### Load a circuit.
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```
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// "myCircuit.cir" is the output of the jaz compiler
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const circuitDef = JSON.parse(fs.readFileSync("myCircuit.cir", "utf8"));
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const circuit = new zkSnark.Circuit(circuitDef);
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```
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### Inspect the circuit.
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```
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// `signalId` can always be a number or an alias string
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circuit.nConstrains; // number of constrains
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circuit.nSignals; // number of signals
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circuit.nPublic; // number of public signals (nOutputs + nPublicInputs)
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// The array of signals is always sorted in this order:
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// [ 1, outputs, publicInputs, privedInputs, internalSignals, constants]
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// returns a,b and c coeficients of the `signalId` on a given `constrain`
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circuit.a(constrain, signalId)
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circuit.b(constrain, signalId)
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circuit.c(constrain, signalId)
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circuit.nOutputs // number of public outputs
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circuit.pubInputs // number of public inputs
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circuit.nPrvInputs // number of private inputs
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circuit.nInputs // number of inputs ( nPublicInputs + nPrivateInputs)
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circuit.nVars // number of variables ( not including constants (one is a variable) )
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circuit.nSignals // number of signals ( including constants )
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circuit.outputIdx(i) // returns the index of the i'th output
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circuit.inputIdx(i) // returns the index of the i'th input
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circuit.pubInputIdx(i) // returns the index of the i'th public input
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circuit.prvInputIdx(i) // returns the index of the i'th private input
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circuit.varIdx(i) // returns the index of the i'th variable
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circuit.constantIdx(i) // returns the index of the i'th constant
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circuit.signalIdx(i) // returns the index of the i'th signal
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// returns signal Idx given a signalId
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// if the idx >= n , it is a constant
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// if the idx == -1, the signal does not exist
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circuit.signalId2idx(signalId);
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// returns an array aliases names for a given signalId
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circuit.signalNames(signalId)
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// input is a key value object where keys are the signal names
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// of all the inputs (public and private)
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// returns an array of values that represent the witness
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circuit.generateWitness(input)
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```
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### Trusted setup
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```
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const setup = zkSnark.setup(circuit);
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fs.writeFileSink("myCircuit.vk_proof", JSON.stringify(setup.vk_proof), "utf8");
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fs.writeFileSink("myCircuit.vk_verifier", JSON.stringify(setup.vk_verifier), "utf8");
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setup.toxic // Must be discarded.
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```
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### Generate proof
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```
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const circuitDef = JSON.parse(fs.readFileSync("myCircuit.cir", "utf8"));
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const circuit = new zkSnark.Circuit(circuitDef);
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const input = {
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"main.pubIn1": "123",
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"main.out1": "456"
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}
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const witness = circuit.generateWitness(input);
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const vk_proof = JSON.parse(fs.readFileSync("myCircuit.vk_proof", "utf8"));
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const {proof, publicSignals} = zkSnark.genProof(vk_proof, witness);
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```
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### Verifier
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```
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const vk_verifier = JSON.parse(fs.readFileSync("myCircuit.vk_verifier", "utf8"));
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if (zkSnark.isValid(vk_verifier, proof, publicSignals)) {
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console.log("The proof is valid");
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} else {
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console.log("The proof is not valid");
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}
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```
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