Implement privkey to ecdsa key

Author: Seongjae Choi

key/key.go

@@ -3,6 +3,8 @@ package key
 import (
 "crypto/ecdsa"
 "crypto/rand"
+"errors"
+"math/big"
 
 "github.com/CodeChain-io/codechain-sdk-go/crypto"
 "github.com/CodeChain-io/codechain-sdk-go/primitives"
@@ -61,3 +63,17 @@ func CreatePlatformAddress(key EcdsaKey, networkID string) (a primitives.Platfor
 
 return primitives.PlatformAddressFromAccountID(hash, networkID)
 }
+
+func ToECDSA(privateKey []byte) (*EcdsaKey, error) {
+priv := new(EcdsaKey)
+priv.PublicKey.Curve = crypto.S256()
+priv.D = new(big.Int).SetBytes(privateKey)
+
+priv.PublicKey.X, priv.PublicKey.Y = priv.PublicKey.Curve.ScalarBaseMult(privateKey)
+
+if priv.PublicKey.X == nil {
+return nil, errors.New("Invalid private key")
+}
+
+return priv, nil
+}