From 5dd19b46ddebc5f6dd54937a4e2b58af7b11ee6e Mon Sep 17 00:00:00 2001
From: arnaucube <root@arnaucube.com>
Date: Wed, 2 Dec 2020 19:57:27 +0100
Subject: [PATCH] Update BabyJubJub EdDSA to last circomlib version

- Update BabyJubJub EdDSA signature to last circomlib version (Poseidon
usage)
- Remove panic on hash error inside verification, to avoid panic due
field overflow of BabyJubJub signature verification
---
 babyjub/eddsa.go      | 8 ++++----
 babyjub/eddsa_test.go | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/babyjub/eddsa.go b/babyjub/eddsa.go
index 8952364..01fdac3 100644
--- a/babyjub/eddsa.go
+++ b/babyjub/eddsa.go
@@ -247,7 +247,7 @@ func (p *PublicKey) VerifyMimc7(msg *big.Int, sig *Signature) bool {
 	hmInput := []*big.Int{sig.R8.X, sig.R8.Y, p.X, p.Y, msg}
 	hm, err := mimc7.Hash(hmInput, nil) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 	if err != nil {
-		panic(err)
+		return false
 	}
 
 	left := NewPoint().Mul(sig.S, B8) // left = s * 8 * B
@@ -273,7 +273,7 @@ func (k *PrivateKey) SignPoseidon(msg *big.Int) *Signature {
 	R8 := NewPoint().Mul(r, B8) // R8 = r * 8 * B
 	A := k.Public().Point()
 
-	hmInput := []*big.Int{R8.X, R8.Y, A.X, A.Y, msg, big.NewInt(int64(0))}
+	hmInput := []*big.Int{R8.X, R8.Y, A.X, A.Y, msg}
 	hm, err := poseidon.Hash(hmInput) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 	if err != nil {
 		panic(err)
@@ -290,10 +290,10 @@ func (k *PrivateKey) SignPoseidon(msg *big.Int) *Signature {
 // VerifyPoseidon verifies the signature of a message encoded as a big.Int in Zq
 // using blake-512 hash for buffer hashing and Poseidon for big.Int hashing.
 func (p *PublicKey) VerifyPoseidon(msg *big.Int, sig *Signature) bool {
-	hmInput := []*big.Int{sig.R8.X, sig.R8.Y, p.X, p.Y, msg, big.NewInt(int64(0))}
+	hmInput := []*big.Int{sig.R8.X, sig.R8.Y, p.X, p.Y, msg}
 	hm, err := poseidon.Hash(hmInput) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 	if err != nil {
-		panic(err)
+		return false
 	}
 
 	left := NewPoint().Mul(sig.S, B8) // left = s * 8 * B
diff --git a/babyjub/eddsa_test.go b/babyjub/eddsa_test.go
index 504beb0..a3813eb 100644
--- a/babyjub/eddsa_test.go
+++ b/babyjub/eddsa_test.go
@@ -96,7 +96,7 @@ func TestSignVerifyPoseidon(t *testing.T) {
 		"15383486972088797283337779941324724402501462225528836549661220478783371668959",
 		sig.R8.Y.String())
 	assert.Equal(t,
-		"1662463587877312619203503803508234533733252768380479199263194005796068211378",
+		"1398758333392199195742243841591064350253744445503462896781493968760929513778",
 		sig.S.String())
 
 	ok := pk.VerifyPoseidon(msg, sig)
@@ -108,7 +108,7 @@ func TestSignVerifyPoseidon(t *testing.T) {
 
 	assert.Equal(t, ""+
 		"dfedb4315d3f2eb4de2d3c510d7a987dcab67089c8ace06308827bf5bcbe02a2"+
-		"b23a1f04909fc088dec7e4835d85a326f7c0d0b2a3d0232d84448ca7c9ebac03",
+		"32f16b0f2f4c4e1169aa59685637e1429b6581a9531d058d65f4ab224eab1703",
 		hex.EncodeToString(sigBuf[:]))
 
 	ok = pk.VerifyPoseidon(msg, sig2)