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go-snark Go Report Card

zkSNARK library implementation in Go

Caution

Implementation from scratch in Go to understand the concepts. Do not use in production.

Not finished, implementing this in my free time to understand it better, so I don't have much time.

Current implementation status:

Usage

Example:

// compile circuit and get the R1CS
flatCode := `
func test(x):
	aux = x*x
	y = aux*x
	z = x + y
	out = z + 5
`

// parse the code
parser := circuitcompiler.NewParser(strings.NewReader(flatCode))
circuit, err := parser.Parse()
assert.Nil(t, err)
fmt.Println(circuit)

// witness
b3 := big.NewInt(int64(3))
inputs := []*big.Int{b3}
w := circuit.CalculateWitness(inputs)
fmt.Println("\nwitness", w)
/*
now we have the witness:
w = [1 3 35 9 27 30]
*/

// flat code to R1CS
fmt.Println("generating R1CS from flat code")
a, b, c := circuit.GenerateR1CS()

/*
now we have the R1CS from the circuit:
a == [[0 1 0 0 0 0] [0 0 0 1 0 0] [0 1 0 0 1 0] [5 0 0 0 0 1]]
b == [[0 1 0 0 0 0] [0 1 0 0 0 0] [1 0 0 0 0 0] [1 0 0 0 0 0]]
c == [[0 0 0 1 0 0] [0 0 0 0 1 0] [0 0 0 0 0 1] [0 0 1 0 0 0]]
*/


alphas, betas, gammas, zx := snark.Utils.PF.R1CSToQAP(a, b, c)


ax, bx, cx, px := snark.Utils.PF.CombinePolynomials(w, alphas, betas, gammas)

hx := snark.Utils.PF.DivisorPolinomial(px, zx)

// hx==px/zx so px==hx*zx
assert.Equal(t, px, snark.Utils.PF.Mul(hx, zx))

// p(x) = a(x) * b(x) - c(x) == h(x) * z(x)
abc := snark.Utils.PF.Sub(pf.Mul(ax, bx), cx)
assert.Equal(t, abc, px)
hz := snark.Utils.PF.Mul(hx, zx)
assert.Equal(t, abc, hz)
	
div, rem := snark.Utils.PF.Div(px, zx)
assert.Equal(t, hx, div)
assert.Equal(t, rem, r1csqap.ArrayOfBigZeros(4))

// calculate trusted setup
setup, err := snark.GenerateTrustedSetup(len(w), circuit, alphas, betas, gammas, zx)
assert.Nil(t, err)
fmt.Println("t", setup.Toxic.T)

// piA = g1 * A(t), piB = g2 * B(t), piC = g1 * C(t), piH = g1 * H(t)
proof, err := snark.GenerateProofs(circuit, setup, hx, w)
assert.Nil(t, err)

assert.True(t, snark.VerifyProof(circuit, setup, proof))

Test

go test ./... -v

Thanks to @jbaylina, @bellesmarta, @adriamb for their explanations that helped to understand this a little bit. Also thanks to @vbuterin for all the published articles explaining the zkSNARKs.