forked from TrueCloudLab/neoneo-go
94 lines
3.8 KiB
Go
94 lines
3.8 KiB
Go
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// Package cubic describes how to create and verify proofs on the Neo
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// blockchain. The example shows how to check that the prover knows the solution
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// of the cubic equation: y = x^3 + x + 5. The example is constructed for
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// BLS12-381 curve points using Groth-16 proving system. The example includes
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// everything that developer needs to start using ZKP on the Neo platform with
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// Go SDK:
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// 1. The described cubic circuit implementation.
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// 2. The off-chain proof generation with the help of gnark-crypto library.
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// 3. The Go verification contract generation and deployment with the help of
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// NeoGo library.
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// 4. The on-chain proof verification for various sets of input data (implemented
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// as end-to-end test).
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// 5. A set of unit-tests aimed to check the circuit validity.
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package cubic
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import (
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"github.com/consensys/gnark-crypto/ecc"
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"github.com/consensys/gnark/backend/groth16"
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"github.com/consensys/gnark/frontend"
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"github.com/consensys/gnark/frontend/cs/r1cs"
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)
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// CubicCircuit defines a simple circuit x**3 + x + 5 == y
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// that checks that the prover knows the solution for the provided expression.
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// The circuit must declare its public and secret inputs as frontend.Variable.
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// At compile time, frontend.Compile(...) recursively parses the struct fields
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// that contains frontend.Variable to build the frontend.constraintSystem.
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// By default, a frontend.Variable has the gnark:",secret" visibility.
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type CubicCircuit struct {
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// Struct tags on a variable is optional.
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// Default uses variable name and secret visibility.
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X frontend.Variable `gnark:"x,secret"` // Secret input.
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Y frontend.Variable `gnark:"y,public"` // Public input.
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}
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// A gnark circuit must implement the frontend.Circuit interface
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// (https://docs.gnark.consensys.net/HowTo/write/circuit_structure).
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var _ = frontend.Circuit(&CubicCircuit{})
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// Define declares the circuit constraints
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// x**3 + x + 5 == y.
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func (circuit *CubicCircuit) Define(api frontend.API) error {
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x3 := api.Mul(circuit.X, circuit.X, circuit.X)
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// Can be used for the circuit debugging.
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api.Println("X^3", x3)
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api.AssertIsEqual(circuit.Y, api.Add(x3, circuit.X, 5))
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return nil
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}
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// main demonstrates how to build the proof and verify it with the help of gnark
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// library. Error handling omitted intentionally to simplify the example.
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func main() {
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var (
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circuit CubicCircuit
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assignment = CubicCircuit{X: 3, Y: 35}
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)
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// Compile our circuit into a R1CS (a constraint system).
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ccs, _ := frontend.Compile(ecc.BLS12_381.ScalarField(), r1cs.NewBuilder, &circuit)
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// Once the circuit is compiled, you can run the three algorithms of a zk-SNARK back end:
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// 1. One time setup (groth16 zkSNARK).
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pk, vk, _ := groth16.Setup(ccs)
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// Intermediate step: witness definition.
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witness, _ := frontend.NewWitness(&assignment, ecc.BLS12_381.ScalarField())
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publicWitness, _ := witness.Public()
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// 2. Proof creation (groth16).
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proof, _ := groth16.Prove(ccs, pk, witness)
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// 3. Proof verification (groth16) via gnark-crypto library.
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_ = groth16.Verify(proof, vk, publicWitness)
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// 4. If building ZKP systems for Neo, you'll need a verification contract
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// deployed to the Neo chain to be able to verify generated proofs. This
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// contract can be generated automatically using NeoGo zkpbinding package:
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// err := zkpbinding.GenerateVerifier(zkpbinding.Config{
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// VerifyingKey: vk,
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// Output: f, // Verifier Go contract writer
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// CfgOutput: fCfg, // Verifier Go contract configuration YAML file
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// GomodOutput: fMod, // go.mod file for the Verifier contract
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// GosumOutput: fSum, // go.sum file for the Verifier contract
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// })
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//
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// Create arguments to invoke `verifyProof` mathod of Verifier contract:
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// verifyProofArgs, err := zkpbinding.GetVerifyProofArgs(proof, publicWitness)
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//
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// For end-to-end usage example, please, see the TestCubicCircuit_EndToEnd test.
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}
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