Add nullifiers objects

Signed-off-by: Jim Zhang <[email protected]>

zkp/golang/internal/utxo/fungible.go

@@ -46,3 +46,28 @@ func (f *Fungible) CalculateIndex() (core.NodeIndex, error) {
 	}
 	return node.NewNodeIndexFromBigInt(hash)
 }
+
+// the "Owner" is the private key that must be properly hashed and trimmed to be
+// compatible with the BabyJub curve.
+// Reference: https://github.com/iden3/circomlib/blob/master/test/babyjub.js#L103
+type FungibleNullifier struct {
+	Amount *big.Int
+	Owner  *big.Int
+	Salt   *big.Int
+}
+
+func NewFungibleNullifier(amount *big.Int, owner *big.Int, salt *big.Int) *FungibleNullifier {
+	return &FungibleNullifier{
+		Amount: amount,
+		Owner:  owner,
+		Salt:   salt,
+	}
+}
+
+func (f *FungibleNullifier) CalculateIndex() (core.NodeIndex, error) {
+	hash, err := poseidon.Hash([]*big.Int{f.Amount, f.Salt, f.Owner})
+	if err != nil {
+		return nil, err
+	}
+	return node.NewNodeIndexFromBigInt(hash)
+}

zkp/golang/internal/utxo/nonfungible.go

@@ -51,6 +51,33 @@ func (f *NonFungible) CalculateIndex() (core.NodeIndex, error) {
 	return node.NewNodeIndexFromBigInt(hash)
 }
 
+// the "Owner" is the private key that must be properly hashed and trimmed to be
+// compatible with the BabyJub curve.
+// Reference: https://github.com/iden3/circomlib/blob/master/test/babyjub.js#L103
+type NonFungibleNullifier struct {
+	TokenId  *big.Int
+	TokenUri *big.Int // hash of the token uri string
+	Owner    *big.Int
+	Salt     *big.Int
+}
+
+func NewNonFungibleNullifier(tokenId, tokenUri *big.Int, owner *big.Int, salt *big.Int) *NonFungibleNullifier {
+	return &NonFungibleNullifier{
+		TokenId:  tokenId,
+		TokenUri: tokenUri,
+		Owner:    owner,
+		Salt:     salt,
+	}
+}
+
+func (f *NonFungibleNullifier) CalculateIndex() (core.NodeIndex, error) {
+	hash, err := poseidon.Hash([]*big.Int{f.TokenId, f.TokenUri, f.Salt, f.Owner})
+	if err != nil {
+		return nil, err
+	}
+	return node.NewNodeIndexFromBigInt(hash)
+}
+
 func HashTokenUri(tokenUri string) (*big.Int, error) {
 	hash := sha256.New()
 	_, err := hash.Write([]byte(tokenUri))

zkp/golang/pkg/utxo/utxo.go

@@ -32,6 +32,14 @@ func NewNonFungible(tokenId, tokenUri *big.Int, owner *babyjub.PublicKey, salt *
 	return utxo.NewNonFungible(tokenId, tokenUri, owner, salt)
 }
 
+func NewFungibleNullifier(amount *big.Int, owner *big.Int, salt *big.Int) core.Indexable {
+	return utxo.NewFungibleNullifier(amount, owner, salt)
+}
+
+func NewNonFungibleNullifier(tokenId *big.Int, tokenUri *big.Int, owner *big.Int, salt *big.Int) core.Indexable {
+	return utxo.NewNonFungibleNullifier(tokenId, tokenUri, owner, salt)
+}
+
 func NewIndexOnly(index core.NodeIndex) core.Indexable {
 	return utxo.NewIndexOnly(index)
 }