feat: added NbG1 and NbG2 apis on groth16 Proving and Verifying keys c…

…loses #116

backend/groth16/groth16.go

@@ -65,6 +65,13 @@ type Proof interface {
 // it's underlying implementation is strongly typed with the curve (see gnark/internal/backend)
 type ProvingKey interface {
 	groth16Object
+
+	// NbG1 returns the number of G1 elements in the ProvingKey
+	NbG1() int
+
+	// NbG2 returns the number of G2 elements in the ProvingKey
+	NbG2() int
+
 	IsDifferent(interface{}) bool
 }
 
@@ -75,9 +82,21 @@ type ProvingKey interface {
 // ExportSolidity is implemented for BN254 and will return an error with other curves
 type VerifyingKey interface {
 	groth16Object
-	NbPublicWitness() int // number of elements expected in the public witness
-	IsDifferent(interface{}) bool
+
+	// NbPublicWitness returns number of elements expected in the public witness
+	NbPublicWitness() int
+
+	// NbG1 returns the number of G1 elements in the VerifyingKey
+	NbG1() int
+
+	// NbG2 returns the number of G2 elements in the VerifyingKey
+	NbG2() int
+
+	// ExportSolidity writes a solidity Verifier contract from the VerifyingKey
+	// this will return an error if not supported on the CurveID()
 	ExportSolidity(w io.Writer) error
+
+	IsDifferent(interface{}) bool
 }
 
 // Verify runs the groth16.Verify algorithm on provided proof with given witness

internal/generator/backend/template/zkpschemes/groth16/groth16.setup.go.tmpl

@@ -420,6 +420,26 @@ func (vk *VerifyingKey) NbPublicWitness() int {
 	return (len(vk.G1.K) - 1)
 }
 
+// NbG1 returns the number of G1 elements in the VerifyingKey
+func (vk *VerifyingKey) NbG1() int {
+	return 3 + len(vk.G1.K)
+}
+
+// NbG2 returns the number of G2 elements in the VerifyingKey
+func (vk *VerifyingKey) NbG2() int {
+	return 3
+}
+
+// NbG1 returns the number of G1 elements in the ProvingKey
+func (pk *ProvingKey) NbG1() int {
+	return 3 + len(pk.G1.A)+ len(pk.G1.B) + len(pk.G1.Z) + len(pk.G1.K)
+}
+
+// NbG2 returns the number of G2 elements in the ProvingKey
+func (pk *ProvingKey) NbG2() int {
+	return 2 + len(pk.G2.B)
+}
+
 // bitRerverse permutation as in fft.BitReverse , but with []curve.G1Affine
 func bitReverse(a []curve.G1Affine) {
 	n := uint(len(a))