add NewPublicKeyFromECDSA

In order to easy import an ethereum like ECDSA public key into a
blindsecp256k1 type public key.

Signed-off-by: p4u <pau@dabax.net>

parsers.go

@@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"math/big"
+
+	"github.com/ethereum/go-ethereum/crypto"
 )
 
 // swapEndianness swaps the order of the bytes in the slice.
@@ -108,6 +110,19 @@ func NewPublicKeyFromBytes(b []byte) (*PublicKey, error) {
 	return &pk, nil
 }
 
+// NewPublicKeyFromECDSA returns a *PublicKey from a serialized/marshaled array
+// of bytes generated by the ethereum/standard ECDSA PubKey implementation.
+func NewPublicKeyFromECDSA(b []byte) (*PublicKey, error) {
+	pub, err := crypto.UnmarshalPubkey(b)
+	if err != nil {
+		return nil, err
+	}
+	pk := new(PublicKey)
+	pk.X = pub.X
+	pk.Y = pub.Y
+	return pk, nil
+}
+
 // MarshalJSON implements the json marshaler for the Signature
 func (sig Signature) MarshalJSON() ([]byte, error) {
 	return json.Marshal(&struct {

parsers_test.go

@@ -6,6 +6,7 @@ import (
 	"math/big"
 	"testing"
 
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -92,3 +93,16 @@ func TestBytes(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, &sig, sig2)
 }
+
+func TestImportECDSApubKey(t *testing.T) {
+	// Generate an ECDSA key
+	k, err := crypto.GenerateKey()
+	assert.Nil(t, err)
+	// Import the ECDSA Public key bytes into a PublicKey type
+	pk, err := NewPublicKeyFromECDSA(crypto.FromECDSAPub(&k.PublicKey))
+	assert.Nil(t, err)
+	// Set the ECDSA Private key point as a blindsecp256k1 PrivateKey type
+	bk := PrivateKey(*k.D)
+	// Compare both public keys
+	assert.Equal(t, bk.Public().Bytes(), pk.Bytes())
+}