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ristretto255
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ristretto255: use multi-model arithmetic

This commit is contained in:
Henry de Valence 2019-05-06 14:30:09 -07:00
parent a360a6556f
commit 0b5e1eb054
3 changed files with 16 additions and 9 deletions
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7
internal/edwards25519/edwards25519.go
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@ -82,6 +82,13 @@ func (v *AffineCached) Zero() *AffineCached {
return v return v
} }
// Assignments.
func (v *ProjP3) Set(u *ProjP3) *ProjP3 {
*v = *u
return v
}
// Conversions. // Conversions.
func (v *ProjP2) FromP1xP1(p *ProjP1xP1) *ProjP2 { func (v *ProjP2) FromP1xP1(p *ProjP1xP1) *ProjP2 {

16
ristretto255.go
View File

@ -35,7 +35,7 @@ var (
// The zero value of Element is not valid, but can be used as the receiver for // The zero value of Element is not valid, but can be used as the receiver for
// any operation. // any operation.
type Element struct { type Element struct {
r edwards25519.ExtendedGroupElement r edwards25519.ProjP3
} }
// Equal returns 1 if e is equivalent to ee, and 0 otherwise. // Equal returns 1 if e is equivalent to ee, and 0 otherwise.
@ -65,18 +65,18 @@ func (e *Element) FromUniformBytes(b []byte) {
f := &radix51.FieldElement{} f := &radix51.FieldElement{}
f.FromBytes(b[:32]) f.FromBytes(b[:32])
p1 := &edwards25519.ExtendedGroupElement{} point1 := &Element{}
mapToPoint(p1, f) mapToPoint(&point1.r, f)
f.FromBytes(b[32:]) f.FromBytes(b[32:])
p2 := &edwards25519.ExtendedGroupElement{} point2 := &Element{}
mapToPoint(p2, f) mapToPoint(&point2.r, f)
e.r.Add(p1, p2) e.Add(point1, point2)
} }
// mapToPoint implements MAP from Section 3.2.4 of draft-hdevalence-cfrg-ristretto-00. // mapToPoint implements MAP from Section 3.2.4 of draft-hdevalence-cfrg-ristretto-00.
func mapToPoint(out *edwards25519.ExtendedGroupElement, t *radix51.FieldElement) { func mapToPoint(out *edwards25519.ProjP3, t *radix51.FieldElement) {
// r = SQRT_M1 * t^2 // r = SQRT_M1 * t^2
r := &radix51.FieldElement{} r := &radix51.FieldElement{}
r.Mul(sqrtM1, r.Square(t)) r.Mul(sqrtM1, r.Square(t))
@ -250,7 +250,7 @@ func (e *Element) Decode(in []byte) error {
// x = CT_ABS(2 * s * den_x) // x = CT_ABS(2 * s * den_x)
// y = u1 * den_y // y = u1 * den_y
// t = x * y // t = x * y
var out edwards25519.ExtendedGroupElement var out edwards25519.ProjP3
out.X.Mul(radix51.Two, s).Mul(&out.X, denX).Abs(&out.X) out.X.Mul(radix51.Two, s).Mul(&out.X, denX).Abs(&out.X)
out.Y.Mul(u1, denY) out.Y.Mul(u1, denY)
out.Z.One() out.Z.One()

2
ristretto255_test.go
View File

@ -71,7 +71,7 @@ var (
compressedRistrettoBasepoint, _ = hex.DecodeString("e2f2ae0a6abc4e71a884a961c500515f58e30b6aa582dd8db6a65945e08d2d76") compressedRistrettoBasepoint, _ = hex.DecodeString("e2f2ae0a6abc4e71a884a961c500515f58e30b6aa582dd8db6a65945e08d2d76")
// The representative Ristretto basepoint in extended coordinates. // The representative Ristretto basepoint in extended coordinates.
ristrettoBasepoint = Element{r: edwards25519.ExtendedGroupElement{ ristrettoBasepoint = Element{r: edwards25519.ProjP3{
X: radix51.FieldElement([5]uint64{426475514619346, 2063872706840040, 14628272888959, 107677749330612, 288339085807592}), X: radix51.FieldElement([5]uint64{426475514619346, 2063872706840040, 14628272888959, 107677749330612, 288339085807592}),
Y: radix51.FieldElement([5]uint64{1934594822876571, 2049809580636559, 1991994783322914, 1758681962032007, 380046701118659}), Y: radix51.FieldElement([5]uint64{1934594822876571, 2049809580636559, 1991994783322914, 1758681962032007, 380046701118659}),
Z: radix51.FieldElement([5]uint64{1, 0, 0, 0, 0}), Z: radix51.FieldElement([5]uint64{1, 0, 0, 0, 0}),