diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..b10e619
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,17 @@
+module kzgceremony
+
+go 1.19
+
+require (
+	github.com/ethereum/go-ethereum v1.10.26
+	github.com/frankban/quicktest v1.14.4
+)
+
+require (
+	github.com/google/go-cmp v0.5.9 // indirect
+	github.com/kr/pretty v0.3.1 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/rogpeppe/go-internal v1.9.0 // indirect
+	golang.org/x/crypto v0.0.0-20210921155107-089bfa567519 // indirect
+	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..dcdad52
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,18 @@
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
+github.com/ethereum/go-ethereum v1.10.26 h1:i/7d9RBBwiXCEuyduBQzJw/mKmnvzsN14jqBmytw72s=
+github.com/ethereum/go-ethereum v1.10.26/go.mod h1:EYFyF19u3ezGLD4RqOkLq+ZCXzYbLoNDdZlMt7kyKFg=
+github.com/frankban/quicktest v1.14.4 h1:g2rn0vABPOOXmZUj+vbmUp0lPoXEMuhTpIluN0XL9UY=
+github.com/frankban/quicktest v1.14.4/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
+github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=
+github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
+github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519 h1:7I4JAnoQBe7ZtJcBaYHi5UtiO8tQHbUSXxL+pnGRANg=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a h1:dGzPydgVsqGcTRVwiLJ1jVbufYwmzD3LfVPLKsKg+0k=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/powersoftau.go b/powersoftau.go
new file mode 100644
index 0000000..301718d
--- /dev/null
+++ b/powersoftau.go
@@ -0,0 +1,79 @@
+package kzgceremony
+
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/crypto/bls12381"
+)
+
+type Contribution struct {
+	SRS *SRS
+}
+
+type SRS struct {
+	G1s []*bls12381.PointG1
+	G2s []*bls12381.PointG2
+}
+
+type toxicWaste struct {
+	tau   *big.Int
+	TauG2 *bls12381.PointG2
+}
+
+// newEmptySRS creates an empty SRS
+func newEmptySRS(nG1, nG2 int) *SRS {
+	g1s := make([]*bls12381.PointG1, nG1)
+	g2s := make([]*bls12381.PointG2, nG2)
+	g1 := bls12381.NewG1()
+	g2 := bls12381.NewG2()
+	// one_G1 := g1.One()
+	// one_G2 := g2.One()
+	for i := 0; i < nG1; i++ {
+		g1s[i] = g1.One()
+		// g1.MulScalar(g1s[i], one_G1, big.NewInt(int64(i)))
+	}
+	for i := 0; i < nG2; i++ {
+		g2s[i] = g2.One()
+		// g2.MulScalar(g2s[i], one_G2, big.NewInt(int64(i)))
+	}
+	return &SRS{g1s, g2s}
+}
+
+func tau(randomness []byte) *toxicWaste {
+	g2 := bls12381.NewG2()
+	tau := new(big.Int).Mod(
+		new(big.Int).SetBytes(randomness),
+		g2.Q())
+	TauG2 := g2.New()
+	g2.MulScalar(TauG2, g2.One(), tau)
+
+	return &toxicWaste{tau, TauG2}
+}
+
+func computeContribution(t *toxicWaste, prevSRS *SRS) *SRS {
+	srs := newEmptySRS(len(prevSRS.G1s), len(prevSRS.G2s))
+	g1 := bls12381.NewG1()
+	g2 := bls12381.NewG2()
+	Q := g1.Q() // Q = |G1| == |G2|
+
+	for i := 0; i < len(prevSRS.G1s); i++ {
+		tau_i := new(big.Int).Exp(t.tau, big.NewInt(int64(i)), Q)
+		g1.MulScalar(srs.G1s[i], prevSRS.G1s[i], tau_i)
+	}
+	for i := 0; i < len(prevSRS.G2s); i++ {
+		tau_i := new(big.Int).Exp(t.tau, big.NewInt(int64(i)), Q)
+		g2.MulScalar(srs.G2s[i], prevSRS.G2s[i], tau_i)
+	}
+
+	return srs
+}
+
+// Contribute
+func Contribute(prevSRS *SRS, randomness []byte) (Contribution, error) {
+	// set tau from randomness
+	tw := tau(randomness)
+
+	newSRS := computeContribution(tw, prevSRS)
+
+	return Contribution{SRS: newSRS}, nil
+}
diff --git a/powersoftau_test.go b/powersoftau_test.go
new file mode 100644
index 0000000..47ec836
--- /dev/null
+++ b/powersoftau_test.go
@@ -0,0 +1,19 @@
+package kzgceremony
+
+import (
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestContribute(t *testing.T) {
+	c := qt.New(t)
+
+	srs_0 := newEmptySRS(10, 10)
+
+	contr_1, err := Contribute(srs_0, []byte("1111111111111111111111111111111111111111111111111111111111111111"))
+	c.Assert(err, qt.IsNil)
+
+	_, err = Contribute(contr_1.SRS, []byte("2222222222222222222222222222222222222222222222222222222222222222"))
+	c.Assert(err, qt.IsNil)
+}