feat: add configurable options for Phase2 MPC setup

backend/groth16/bn254/mpcsetup/phase2_options.go

@@ -0,0 +1,25 @@
+package mpcsetup
+
+import (
+	"crypto/rand"
+	"io"
+)
+
+// Phase2Options contains configuration options for Phase2
+type Phase2Options struct {
+	// RandomSource is the source of randomness for contribution generation
+	RandomSource io.Reader
+}
+
+// DefaultPhase2Options returns default options for Phase2
+func DefaultPhase2Options() *Phase2Options {
+	return &Phase2Options{
+		RandomSource: rand.Reader,
+	}
+}
+
+// WithRandomSource sets a custom random source for Phase2Options
+func (o *Phase2Options) WithRandomSource(source io.Reader) *Phase2Options {
+	o.RandomSource = source
+	return o
+}

backend/groth16/bn254/mpcsetup/phase2_test.go

@@ -0,0 +1,51 @@
+package mpcsetup
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPhase2WithCustomRandomSource(t *testing.T) {
+	// Create a test random source
+	testRandomSource := bytes.NewReader(make([]byte, 32))
+
+	// Create options with custom random source
+	options := DefaultPhase2Options().WithRandomSource(testRandomSource)
+
+	// Create a new Phase2 instance with options
+	phase2 := NewPhase2(options)
+
+	// Check that options are set correctly
+	assert.NotNil(t, phase2.options)
+	assert.Equal(t, testRandomSource, phase2.options.RandomSource)
+
+	// Generate contribution
+	err := phase2.GenerateContribution()
+	require.NoError(t, err)
+
+	// Check that contribution was generated
+	assert.NotNil(t, phase2.Parameters)
+	assert.NotNil(t, phase2.Parameters.G1.Delta)
+	assert.NotNil(t, phase2.Parameters.G2.Delta)
+}
+
+func TestPhase2WithDefaultOptions(t *testing.T) {
+	// Create Phase2 with default options
+	phase2 := NewPhase2(nil)
+
+	// Check that default options are set
+	assert.NotNil(t, phase2.options)
+	assert.NotNil(t, phase2.options.RandomSource)
+
+	// Generate contribution
+	err := phase2.GenerateContribution()
+	require.NoError(t, err)
+
+	// Check that contribution was generated
+	assert.NotNil(t, phase2.Parameters)
+	assert.NotNil(t, phase2.Parameters.G1.Delta)
+	assert.NotNil(t, phase2.Parameters.G2.Delta)
+}

backend/groth16/bn254/mpcsetup/unsafe.go

@@ -0,0 +1,82 @@
+// Copyright 2020-2025 Consensys Software Inc.
+// Licensed under the Apache License, Version 2.0. See the LICENSE file for details.
+
+package mpcsetup
+
+import (
+	"encoding/binary"
+	"io"
+
+	curve "github.com/consensys/gnark-crypto/ecc/bn254"
+	"github.com/consensys/gnark-crypto/ecc/bn254/mpcsetup"
+	gIo "github.com/consensys/gnark/io"
+)
+
+// UnsafeReadFrom implements io.UnsafeReaderFrom
+func (p *Phase2) UnsafeReadFrom(reader io.Reader) (n int64, err error) {
+	var nbCommitments uint16
+
+	if err = binary.Read(reader, binary.BigEndian, &nbCommitments); err != nil {
+		return -1, err
+	}
+	n = 2
+
+	p.Sigmas = make([]mpcsetup.UpdateProof, nbCommitments)
+	p.Parameters.G1.SigmaCKK = make([][]curve.G1Affine, nbCommitments)
+	p.Parameters.G2.Sigma = make([]curve.G2Affine, nbCommitments)
+
+	dec := curve.NewDecoder(reader)
+	for _, v := range p.refsSlice() {
+		if err = dec.Decode(v); err != nil {
+			return n + dec.BytesRead(), err
+		}
+	}
+
+	if err = dec.Decode(&p.Delta); err != nil {
+		return n + dec.BytesRead(), err
+	}
+
+	for i := range p.Sigmas {
+		if err = dec.Decode(&p.Sigmas[i]); err != nil {
+			return n + dec.BytesRead(), err
+		}
+	}
+
+	challenge, dn, err := gIo.ReadBytesShort(reader)
+	if err != nil {
+		return n + dec.BytesRead() + dn, err
+	}
+	p.Challenge = challenge
+	return n + dec.BytesRead() + dn, nil
+}
+
+// BinaryDump implements io.BinaryDumper
+func (p *Phase2) BinaryDump(writer io.Writer) (n int64, err error) {
+	if err = binary.Write(writer, binary.BigEndian, uint16(len(p.Parameters.G2.Sigma))); err != nil {
+		return -1, err
+	}
+	n = 2
+
+	enc := curve.NewEncoder(writer)
+	for _, v := range p.refsSlice() {
+		if err = enc.Encode(v); err != nil {
+			return n + enc.BytesWritten(), err
+		}
+	}
+
+	if err = enc.Encode(&p.Delta); err != nil {
+		return n + enc.BytesWritten(), err
+	}
+
+	for i := range p.Sigmas {
+		if err = enc.Encode(&p.Sigmas[i]); err != nil {
+			return n + enc.BytesWritten(), err
+		}
+	}
+
+	dn, err := gIo.WriteBytesShort(p.Challenge, writer)
+	if err != nil {
+		return n + enc.BytesWritten() + dn, err
+	}
+	return n + enc.BytesWritten() + dn, nil
+}