refactor: write encrypt bls key to string

crypto/bls/attestation.go

@@ -186,6 +186,24 @@ func GenRandomBlsKeys() (*KeyPair, error) {
 
 // SaveToFile saves the private key in an encrypted keystore file
 func (k *KeyPair) SaveToFile(path string, password string) error {
+	data, err := k.EncryptedString(path, password)
+	if err != nil {
+		return err
+	}
+
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		fmt.Println("Error creating directories:", err)
+		return err
+	}
+	err = os.WriteFile(path, data, 0644)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (k *KeyPair) EncryptedString(path string, password string) ([]byte, error) {
 	sk32Bytes := k.PrivKey.Bytes()
 	skBytes := make([]byte, 32)
 	for i := 0; i < 32; i++ {
@@ -199,7 +217,7 @@ func (k *KeyPair) SaveToFile(path string, password string) error {
 		keystore.StandardScryptP,
 	)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	encryptedBLSStruct := encryptedBLSKeyJSONV3{
@@ -208,19 +226,9 @@ func (k *KeyPair) SaveToFile(path string, password string) error {
 	}
 	data, err := json.Marshal(encryptedBLSStruct)
 	if err != nil {
-		return err
-	}
-
-	dir := filepath.Dir(path)
-	if err := os.MkdirAll(dir, 0755); err != nil {
-		fmt.Println("Error creating directories:", err)
-		return err
-	}
-	err = os.WriteFile(path, data, 0644)
-	if err != nil {
-		return err
+		return nil, err
 	}
-	return nil
+	return data, nil
 }
 
 func ReadPrivateKeyFromFile(path string, password string) (*KeyPair, error) {