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return error if no ModSqrt(x, q) exist in babyjubjub decompress point

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arnaucube
2019-09-10 00:36:54 +02:00
parent c95c95b7b1
commit a60e154d86
1 changed files with 4 additions and 1 deletions
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5
babyjub/babyjub.go
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@@ -203,7 +203,10 @@ func (p *Point) Decompress(leBuf [32]byte) (*Point, error) {
xb.ModInverse(xb, constants.Q)
p.X.Mul(xa, xb) // xa / xb
p.X.Mod(p.X, constants.Q)
p.X.ModSqrt(p.X, constants.Q)
noSqrt := p.X.ModSqrt(p.X, constants.Q)
if noSqrt == nil {
return nil, fmt.Errorf("x is not a square mod q")
}
if (sign && !PointCoordSign(p.X)) || (!sign && PointCoordSign(p.X)) {
p.X.Mul(p.X, constants.MinusOne)
}