srs.go

package main

import (
	"errors"
	"fmt"
	"io"
	"os"

	"github.com/consensys/gnark-crypto/ecc/bn254"
	"github.com/consensys/gnark-crypto/ecc/bn254/fr"
	"github.com/consensys/gnark-crypto/ecc/bn254/kzg"
)

func TestSRS(srsFilePath string) error {
	srsFile, err := os.Open(srsFilePath)
	if err != nil {
		return fmt.Errorf("failed to open SRS file '%s': %w", srsFilePath, err)
	}
	defer srsFile.Close()

	var srs kzg.SRS
	bytesRead, err := srs.ReadFrom(srsFile)
	if err != nil {
		if errors.Is(err, io.ErrUnexpectedEOF) || errors.Is(err, io.EOF) {
			return fmt.Errorf("failed to read full SRS from '%s': file may be too short or corrupted. Read %d bytes. Error: %w", srsFilePath, bytesRead, err)
		}
		return fmt.Errorf("failed to read/deserialize SRS from '%s': %w", srsFilePath, err)
	}

	numG1Points := uint64(len(srs.Pk.G1))
	if numG1Points == 0 {
		return fmt.Errorf("SRS Proving Key (Pk.G1) has no G1 points")
	}
	srsMaxDegree := numG1Points - 1

	if len(srs.Vk.G2) < 2 {
		return fmt.Errorf("SRS Verifying Key (Vk.G2) has %d points, expected at least 2 ([G2, alpha*G2])", len(srs.Vk.G2))
	}

	var g1Zero bn254.G1Affine
	if srs.Vk.G1.Equal(&g1Zero) {
		return fmt.Errorf("SRS Verifying Key G1 generator (Vk.G1) is the zero point")
	}

	var testDegree := int 3

	if numG1Points < uint64(testDegree+1) {
		testDegree = int(srsMaxDegree)
	}

	poly := make([]fr.Element, testDegree+1)
	for i := 0; i <= testDegree; i++ {
		poly[i].SetUint64(uint64(i + 1))
	}

	digest, err := kzg.Commit(poly, srs.Pk)
	if err != nil {
		return fmt.Errorf("failed to commit to polynomial: %w", err)
	}

	var point fr.Element
	point.SetString("12345")

	openingProof, err := kzg.Open(poly, point, srs.Pk)
	if err != nil {
		return fmt.Errorf("failed to generate opening proof: %w", err)
	}

	err = kzg.Verify(&digest, &openingProof, point, srs.Vk)
	if err != nil {
		return fmt.Errorf("verification of opening proof failed: %w", err)
	}

	return nil
}

func main() {
	srsFilePath := os.Args[1]

	err := TestSRS(srsFilePath)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error testing SRS '%s': %v\n", srsFilePath, err)
		os.Exit(1)
	}

	fmt.Printf("SRS file '%s' tested successfully.\n", srsFilePath)
}