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Merge pull request #26 from iden3/feature/pointfromsigny

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Babyjubjub separate PointFromSignAndY from p.Decompress
This commit is contained in:
Eduard S
2020-08-06 13:50:47 +02:00
committed by GitHub
parent 29a66457f0 833f68a614
commit 327a8175d6
2 changed files with 23 additions and 1 deletions
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10
babyjub/babyjub.go
View File

@@ -181,6 +181,14 @@ func (p *Point) Decompress(leBuf [32]byte) (*Point, error) {
leBuf[31] = leBuf[31] & 0x7F
}
utils.SetBigIntFromLEBytes(p.Y, leBuf[:])
return PointFromSignAndY(sign, p.Y)
}
// PointFromSignAndY returns a Point from a Sign and the Y coordinate
func PointFromSignAndY(sign bool, y *big.Int) (*Point, error) {
var p Point
p.X = big.NewInt(0)
p.Y = y
if p.Y.Cmp(constants.Q) >= 0 {
return nil, fmt.Errorf("p.y >= Q")
}
@@ -209,5 +217,5 @@ func (p *Point) Decompress(leBuf [32]byte) (*Point, error) {
}
p.X.Mod(p.X, constants.Q)
return p, nil
return &p, nil
}

14
babyjub/babyjub_test.go
View File

@@ -192,6 +192,20 @@ func TestInSubGroup2(t *testing.T) {
assert.Equal(t, true, p.InSubGroup())
}
func TestPointFromSignAndy(t *testing.T) {
x := utils.NewIntFromString(
"17777552123799933955779906779655732241715742912184938656739573121738514868268")
y := utils.NewIntFromString(
"2626589144620713026669568689430873010625803728049924121243784502389097019475")
p := &Point{X: x, Y: y}
sign := PointCoordSign(p.X)
p2, err := PointFromSignAndY(sign, p.Y)
assert.Equal(t, nil, err)
assert.Equal(t, p.X.String(), p2.X.String())
assert.Equal(t, p.Y.String(), p2.Y.String())
}
func TestCompressDecompress1(t *testing.T) {
x := utils.NewIntFromString(
"17777552123799933955779906779655732241715742912184938656739573121738514868268")