Add SetUint64 to Group.Scalar.

Author: armfazh

group/group.go

@@ -45,6 +45,7 @@ type Element interface {
 // Scalar represents an integer scalar.
 type Scalar interface {
 	IsEqual(Scalar) bool
+	SetUint64(uint64)
 	Add(Scalar, Scalar) Scalar
 	Sub(Scalar, Scalar) Scalar
 	Mul(Scalar, Scalar) Scalar

group/group_test.go

@@ -183,18 +183,22 @@ func testScalar(t *testing.T, testTimes int, g group.Group) {
 	d := g.NewScalar()
 	e := g.NewScalar()
 	f := g.NewScalar()
+	one := g.NewScalar()
+	one.SetUint64(1)
 	params := g.Params()
 	for i := 0; i < testTimes; i++ {
 		a := g.RandomScalar(rand.Reader)
 		b := g.RandomScalar(rand.Reader)
 		c.Add(a, b)
 		d.Sub(a, b)
 		e.Mul(c, d)
+		e.Add(e, one)
 
 		c.Mul(a, a)
 		d.Mul(b, b)
 		d.Neg(d)
 		f.Add(c, d)
+		f.Add(f, one)
 		enc1, err1 := e.MarshalBinary()
 		enc2, err2 := f.MarshalBinary()
 		if err1 != nil || err2 != nil || !bytes.Equal(enc1, enc2) {
@@ -204,6 +208,13 @@ func testScalar(t *testing.T, testTimes int, g group.Group) {
 			test.ReportError(t, l, params.ScalarLength)
 		}
 	}
+
+	a := g.RandomScalar(rand.Reader)
+	c.Inv(a)
+	c.Mul(c, a)
+	if !one.IsEqual(c) {
+		test.ReportError(t, c, one, a)
+	}
 }
 
 func BenchmarkElement(b *testing.B) {

group/ristretto255.go

@@ -4,6 +4,7 @@ import (
 	"crypto"
 	_ "crypto/sha512" // to link libraries
 	"io"
+	"math/big"
 
 	r255 "github.com/bwesterb/go-ristretto"
 )
@@ -145,6 +146,8 @@ func (e *ristrettoElement) UnmarshalBinary(data []byte) error {
 	return e.p.UnmarshalBinary(data)
 }
 
+func (s *ristrettoScalar) SetUint64(n uint64) { s.s.SetBigInt(new(big.Int).SetUint64(n)) }
+
 func (s *ristrettoScalar) IsEqual(x Scalar) bool {
 	return s.s.Equals(&x.(*ristrettoScalar).s)
 }

group/short.go

@@ -195,7 +195,8 @@ type wScl struct {
 	k []byte
 }
 
-func (s *wScl) String() string { return fmt.Sprintf("0x%x", s.k) }
+func (s *wScl) String() string     { return fmt.Sprintf("0x%x", s.k) }
+func (s *wScl) SetUint64(n uint64) { s.fromBig(new(big.Int).SetUint64(n)) }
 func (s *wScl) IsEqual(a Scalar) bool {
 	aa := s.cvtScl(a)
 	return subtle.ConstantTimeCompare(s.k, aa.k) == 1