2 files changed, 30 insertions, 5 deletions
diff --git a/nizk/commit/commit.go b/nizk/commit/commit.go
index 84ba8e5..1fa653e 100644
--- a/nizk/commit/commit.go
+++ b/nizk/commit/commit.go
@@ -13,8 +13,8 @@ import (
 
 type Statement struct {
 	bitSet bool
-	a    *Scalar
-	b    *Scalar
+	a      *Scalar
+	b      *Scalar
 	Commitment
 }
 
@@ -25,11 +25,16 @@ type Commitment struct {
 	Proof *Proof
 }
 
-func NewStatement(a, b *Scalar, bitSet bool) *Statement {
+func NewStatement(bitSet bool) *Statement {
+	a, b := Curve.RandomScalar(), Curve.RandomScalar()
+	return NewStatementFromScalars(bitSet, a, b)
+}
+
+func NewStatementFromScalars(bitSet bool, a, b *Scalar) *Statement {
 	return &Statement{
 		a:          a,
 		b:          b,
-		bitSet:       bitSet,
+		bitSet:     bitSet,
 		Commitment: commitment(a, b, bitSet),
 	}
 }
diff --git a/nizk/commit/commit_test.go b/nizk/commit/commit_test.go
index 8763706..4ea5964 100644
--- a/nizk/commit/commit_test.go
+++ b/nizk/commit/commit_test.go
@@ -7,11 +7,31 @@ import (
 )
 
 func TestStatement(t *testing.T) {
+	id := Curve.RandomScalar()
+	Id := G.Exp(id)
+
+	st1, st2 := NewStatement(true), NewStatement(false)
+	c1, c2 := st1.Commit(Id), st2.Commit(Id)
+	if !c1.Verify() {
+		t.Fatal("Could not verify st1 with c1, plus=true case")
+	}
+	if !c2.Verify() {
+		t.Fatal("Could not verify st2 with c2, plus=false case")
+	}
+
+	// Use the wrong proof
+	c2.Proof = c1.Proof
+	if c2.Verify() {
+		t.Fatal("Verify with wrong proof should have failed!")
+	}
+}
+
+func TestStatementFromScalar(t *testing.T) {
 	var α, β, id = Curve.RandomScalar(), Curve.RandomScalar(), Curve.RandomScalar()
 
 	Id := G.Exp(id)
 
-	st1, st2 := NewStatement(α, β, true), NewStatement(α, β, false)
+	st1, st2 := NewStatementFromScalars(true, α, β), NewStatementFromScalars(false, α, β)
 	c1, c2 := st1.Commit(Id), st2.Commit(Id)
 	if !c1.Verify() {
 		t.Fatal("Could not verify st1 with c1, plus=true case")