remove pvss delta

Author: txhsl

dkg.go

@@ -189,7 +189,7 @@ func (p *Participant) GenerateSecret(threshold int) {
 }
 
 func (p *Participant) RenovateSecret() {
-	p.secret.BiasDelta()
+	p.secret.Renovate()
 }
 
 func (p *Participant) GenerateShares(size int) []*bls.Fr {

encryption.go

@@ -55,11 +55,16 @@ func AESDecrypt(pg1 *bls.PointG1, cipherText []byte) ([]byte, error) {
 	return result, nil
 }
 
-func RandPG1() *bls.PointG1 {
+func RandScalar() *bls.Fr {
 	s1 := rand.NewSource(time.Now().UnixNano())
 	r1 := rand.New(s1)
 	r, _ := bls.NewFr().Rand(r1)
+
+	return r
+}
+
+func RandPG1() *bls.PointG1 {
 	g1 := bls.NewG1()
 	pg1 := g1.New()
-	return g1.MulScalar(pg1, &bls.G1One, r)
+	return g1.MulScalar(pg1, &bls.G1One, RandScalar())
 }

public_key.go

@@ -2,8 +2,6 @@ package tpke
 
 import (
 	"math/big"
-	"math/rand"
-	"time"
 
 	bls "github.com/kilic/bls12-381"
 )
@@ -26,9 +24,7 @@ func NewGlobalPublicKey(cs []*Commitment, scaler int) *PublicKey {
 }
 
 func (pk *PublicKey) Encrypt(msg *bls.PointG1) *CipherText {
-	s1 := rand.NewSource(time.Now().UnixNano())
-	r1 := rand.New(s1)
-	r, _ := bls.NewFr().Rand(r1)
+	r := RandScalar()
 
 	// C=M+rpk, R1=rG1, R2=rG2
 	g1 := bls.NewG1()

pvss.go

@@ -11,18 +11,15 @@ type PVSS struct {
 	r1         *bls.PointG1
 	r2         *bls.PointG2
 	bigf       []*bls.PointG1
-	delta      *bls.PointG1
 }
 
 func GenerateSharedSecrets(r *bls.Fr, size int, secret *Secret) (*PVSS, []*bls.Fr) {
 	g1 := bls.NewG1()
 	g2 := bls.NewG2()
 	r1 := g1.New()
 	r2 := g2.New()
-	delta := g1.New()
 	g1.MulScalar(r1, &bls.G1One, r)
 	g2.MulScalar(r2, &bls.G2One, r)
-	g1.MulScalar(delta, &bls.G1One, secret.delta)
 	f := make([]*bls.Fr, size)
 	bigf := make([]*bls.PointG1, size)
 	for i := 0; i < size; i++ {
@@ -38,7 +35,6 @@ func GenerateSharedSecrets(r *bls.Fr, size int, secret *Secret) (*PVSS, []*bls.F
 		r1:         r1,
 		r2:         r2,
 		bigf:       bigf,
-		delta:      delta,
 	}, f
 }
 
@@ -70,16 +66,5 @@ func (pvss *PVSS) VerifyRenovate(op *PVSS) bool {
 		return false
 	}
 	g1 := bls.NewG1()
-	for i := range pvss.commitment.coeff {
-		if i == 0 {
-			if !g1.Equal(pvss.commitment.coeff[i], op.commitment.coeff[i]) {
-				return false
-			}
-		} else {
-			if !g1.Equal(pvss.commitment.coeff[i], g1.Add(g1.Zero(), op.commitment.coeff[i], pvss.delta)) {
-				return false
-			}
-		}
-	}
-	return true
+	return g1.Equal(pvss.commitment.coeff[0], op.commitment.coeff[0])
 }

secrect.go

@@ -1,9 +1,6 @@
 package tpke
 
 import (
-	"math/rand"
-	"time"
-
 	bls "github.com/kilic/bls12-381"
 )
 
@@ -19,20 +16,14 @@ func RandomSecret(threshold int) *Secret {
 	}
 }
 
-func (s *Secret) BiasDelta() {
-	// generate a random bias
-	source := rand.NewSource(time.Now().UnixNano())
-	random := rand.New(source)
-	delta, _ := bls.NewFr().Rand(random)
-
+func (s *Secret) Renovate() {
 	// add bias to a1..an-1 expect a0
 	for i := range s.poly.coeff {
 		if i == 0 {
 			continue
 		}
-		s.poly.coeff[i].Add(s.poly.coeff[i], delta)
+		s.poly.coeff[i].Set(RandScalar())
 	}
-	s.delta = delta
 }
 
 func (s *Secret) Commitment() *Commitment {