Merge pull request #3234 from nspcc-dev/add-response-source
examples: improve cubic circuit documentation
This commit is contained in:
Roman Khimov
GitHub
commit
e8e964e3da
2 changed files with 33 additions and 15 deletions
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@ -31,20 +31,25 @@ to organize the ceremony and generate proving and verifying keys for a circuit.
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However, both phases take a significant amount of time and computations to be
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performed. Luckily for the developers, it is possible to omit a curve-specific
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part of the MPC and reuse the existing results of Phase 1 got from a trusted
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source, e.g. from [Powers of Tau ceremony](https://github.com/filecoin-project/powersoftau/)
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held by the [Filecoin project](https://github.com/filecoin-project/phase2-attestations#phase1).
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source, e.g. from [Zcash PowersOfTau](https://github.com/ZcashFoundation/powersoftau-attestations)
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held by the [Zcash Foundation](https://github.com/ZcashFoundation).
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`TestCubicCircuit_EndToEnd_Prod` test of the current circuit example demonstrates
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how to use the `response` output file from the Phase 1 of the Filecoin's Powers
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of Tau ceremony for BLS12-381 curve:
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* [`response8`](./response8) file is the response output from the [Powers of Tau ceremony](https://github.com/filecoin-project/powersoftau/)
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with the `REQUIRED_POWER` set to 8 (to reduce computations and response file size)
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that was run locally with the help of [testing script](https://github.com/filecoin-project/powersoftau/blob/master/test.sh).
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* [`response8`](./response8) file is the response output from the ceremony that was run locally
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based on the [Filecoin Powers of Tau](https://github.com/filecoin-project/powersoftau/)
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with the `REQUIRED_POWER` set to 8 (to reduce computations and response file size).
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The ceremony itself was run with the help of [testing script](https://github.com/filecoin-project/powersoftau/blob/master/test.sh).
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To get the response file for a production environment, the user has two options:
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1. Organize his own ceremony with required number of powers following the
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[guide](https://github.com/filecoin-project/powersoftau/tree/master#instructions)
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from the source repo.
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2. Download the existing suitable `response` file from the
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[attestations page](https://github.com/arielgabizon/perpetualpowersoftau#perpetual-powers-of-tau-for-bls381).
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from the ceremony source repo.
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2. Download the existing suitable `response` file from the trusted existing ceremony.
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Please, be careful while choosing `response` file and ensure that it has enough
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powers computed (at least as much as the number of the circuit's constraints requires).
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Example of suitable ceremonies:
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* Zcash Powers Of Tau [attestations page](https://github.com/ZcashFoundation/powersoftau-attestations) (up to 2^21)
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* Filecoin Perpetual Powers Of Tau [attestations page](https://github.com/arielgabizon/perpetualpowersoftau#perpetual-powers-of-tau-for-bls381) (up to 2^27)
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* [main_test](./main_test.go) contains the `TestCubicCircuit_EndToEnd_Prod` test
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itself and demonstrates how to properly initialize Phase 2 based on the given
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response file and make some dummy contributions into it.
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@ -1,6 +1,7 @@
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package cubic
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import (
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"fmt"
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"math"
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"os"
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"path/filepath"
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@ -156,6 +157,12 @@ func TestCubicCircuit_EndToEnd(t *testing.T) {
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// result for proving/verifying keys generation and demonstrates how to contribute
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// some randomness into it.
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func TestCubicCircuit_EndToEnd_Prod(t *testing.T) {
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const (
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// Response file generated locally for 2^8 powers.
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pathToResponseFile = "./response8"
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// The order of Powers of Tau ceremony, it depends on the response file.
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orderOfResponseFile = 8
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)
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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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@ -166,8 +173,10 @@ func TestCubicCircuit_EndToEnd_Prod(t *testing.T) {
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require.NoError(t, err)
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// Setup (groth16 zkSNARK), use MPC-based solution for proving and verifying
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// keys generation.
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pk, vk := setup(t, ccs, "./response8", 8) // the order of Powers of Tau ceremony, depends on the response file.
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// keys generation. Please, be careful while adopting this code for your circuit.
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// Ensure that response file that you've provided contains enough powers computed
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// so that the number of constraints in your circuit can be handled.
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pk, vk := setup(t, ccs, pathToResponseFile, orderOfResponseFile)
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// Intermediate step: witness definition.
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witness, err := frontend.NewWitness(&assignment, ecc.BLS12_381.ScalarField())
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@ -262,20 +271,21 @@ func setup(t *testing.T, ccs constraint.ConstraintSystem, phase1ResponsePath str
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beta_coef_g1 := make([]curve.G1Affine, inN)
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// Accumulator serialization: https://github.com/filecoin-project/powersoftau/blob/ab8f85c28f04af5a99cfcc93a3b1f74c06f94105/src/accumulator.rs#L111
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errMessage := fmt.Sprintf("ensure your response file contains exactly 2^%d powers of tau for BLS12-381 curve", inPow)
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for i := range coef_g1 {
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require.NoError(t, dec.Decode(&coef_g1[i]))
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require.NoError(t, dec.Decode(&coef_g1[i]), errMessage)
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}
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for i := range coef_g2 {
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require.NoError(t, dec.Decode(&coef_g2[i]))
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require.NoError(t, dec.Decode(&coef_g2[i]), errMessage)
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}
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for i := range alpha_coef_g1 {
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require.NoError(t, dec.Decode(&alpha_coef_g1[i]))
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require.NoError(t, dec.Decode(&alpha_coef_g1[i]), errMessage)
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}
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for i := range beta_coef_g1 {
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require.NoError(t, dec.Decode(&beta_coef_g1[i]))
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require.NoError(t, dec.Decode(&beta_coef_g1[i]), errMessage)
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}
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beta_g2 := &curve.G2Affine{}
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require.NoError(t, dec.Decode(beta_g2))
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require.NoError(t, dec.Decode(beta_g2), errMessage)
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// Transform (take exactly those number of powers that needed for the given number of constraints).
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var (
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@ -286,6 +296,9 @@ func setup(t *testing.T, ccs constraint.ConstraintSystem, phase1ResponsePath str
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}
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outN := int64(math.Pow(2, float64(outPow)))
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if len(coef_g1) < int(2*outN-1) {
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t.Fatalf("number of circuit constraints is too large for the provided response file: nbConstraints is %d, required at least %d powers to be computed", numConstraints, outN)
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}
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srs1 := mpcsetup.Phase1{}
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srs1.Parameters.G1.Tau = coef_g1[:2*outN-1] // outN + (outN-1)
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srs1.Parameters.G2.Tau = coef_g2[:outN] // outN
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