1# go-snark [![Go Report Card](https://goreportcard.com/badge/github.com/arnaucube/go-snark)](https://goreportcard.com/report/github.com/arnaucube/go-snark)
 2
 3zkSNARK library implementation in Go
 4
 5
 6- `Succinct Non-Interactive Zero Knowledge for a von Neumann Architecture`, Eli Ben-Sasson, Alessandro Chiesa, Eran Tromer, Madars Virza https://eprint.iacr.org/2013/879.pdf
 7- `Pinocchio: Nearly practical verifiable computation`, Bryan Parno, Craig Gentry, Jon Howell, Mariana Raykova https://eprint.iacr.org/2013/279.pdf
 8
 9## Caution
10Implementation from scratch in Go to understand the concepts. Do not use in production.
11
12Not finished, implementing this in my free time to understand it better, so I don't have much time.
13
14
15### Usage
16- [![GoDoc](https://godoc.org/github.com/arnaucube/go-snark?status.svg)](https://godoc.org/github.com/arnaucube/go-snark) zkSnark
17- [![GoDoc](https://godoc.org/github.com/arnaucube/go-snark/bn128?status.svg)](https://godoc.org/github.com/arnaucube/go-snark/bn128) bn128 (more details: https://github.com/arnaucube/go-snark/tree/master/bn128)
18- [![GoDoc](https://godoc.org/github.com/arnaucube/go-snark/fields?status.svg)](https://godoc.org/github.com/arnaucube/go-snark/fields) Finite Fields operations
19- [![GoDoc](https://godoc.org/github.com/arnaucube/go-snark/r1csqap?status.svg)](https://godoc.org/github.com/arnaucube/go-snark/r1csqap) R1CS to QAP (more details: https://github.com/arnaucube/go-snark/tree/master/r1csqap)
20- [![GoDoc](https://godoc.org/github.com/arnaucube/go-snark/circuitcompiler?status.svg)](https://godoc.org/github.com/arnaucube/go-snark/circuitcompiler) Circuit Compiler
21
22Example:
23```go
24bn, err := bn128.NewBn128()
25assert.Nil(t, err)
26
27// new Finite Field
28fqR := fields.NewFq(bn.R)
29
30// new Polynomial Field
31pf := r1csqap.NewPolynomialField(f)
32
33/*
34suppose that we have the following variables with *big.Int elements:
35a = [[0 1 0 0 0 0] [0 0 0 1 0 0] [0 1 0 0 1 0] [5 0 0 0 0 1]]
36b = [[0 1 0 0 0 0] [0 1 0 0 0 0] [1 0 0 0 0 0] [1 0 0 0 0 0]]
37c = [[0 0 0 1 0 0] [0 0 0 0 1 0] [0 0 0 0 0 1] [0 0 1 0 0 0]]
38
39w = [1, 3, 35, 9, 27, 30]
40*/
41
42alphas, betas, gammas, zx := pf.R1CSToQAP(a, b, c)
43
44// wittness = 1, 3, 35, 9, 27, 30
45w := []*big.Int{b1, b3, b35, b9, b27, b30}
46circuit := compiler.Circuit{
47	NVars:    6,
48	NPublic:  0,
49	NSignals: len(w),
50}
51ax, bx, cx, px := pf.CombinePolynomials(w, alphas, betas, gammas)
52
53hx := pf.DivisorPolinomial(px, zx)
54
55// hx==px/zx so px==hx*zx
56assert.Equal(t, px, pf.Mul(hx, zx))
57
58// p(x) = a(x) * b(x) - c(x) == h(x) * z(x)
59abc := pf.Sub(pf.Mul(ax, bx), cx)
60assert.Equal(t, abc, px)
61hz := pf.Mul(hx, zx)
62assert.Equal(t, abc, hz)
63	
64div, rem := pf.Div(px, zx)
65assert.Equal(t, hx, div)
66assert.Equal(t, rem, r1csqap.ArrayOfBigZeros(4))
67
68// calculate trusted setup
69setup, err := GenerateTrustedSetup(bn, fqR, pf, len(w), circuit, alphas, betas, gammas, zx)
70assert.Nil(t, err)
71fmt.Println("t", setup.Toxic.T)
72
73// piA = g1 * A(t), piB = g2 * B(t), piC = g1 * C(t), piH = g1 * H(t)
74proof, err := GenerateProofs(bn, fqR, circuit, setup, hx, w)
75assert.Nil(t, err)
76
77assert.True(t, VerifyProof(bn, circuit, setup, proof))
78```
79
80### Test
81```
82go test ./... -v
83```
84
85---
86
87
88Thanks to [@jbaylina](https://github.com/jbaylina), [@bellesmarta](https://github.com/bellesmarta), [@adriamb](https://github.com/adriamb) for their explanations that helped to understand this a little bit. Also thanks to [@vbuterin](https://github.com/vbuterin) for all the published articles explaining the zkSNARKs.