func ToPrivateKey(keyB64 Base64String, auth string) (*ecdsa.PrivateKey, error) {
	keyjson, err := ToBytes(keyB64)
	if err != nil {
		return nil, err
	}
	key, err := keystore.DecryptKey(keyjson, auth)
	if err != nil {
		return nil, err
	}
	return key.PrivateKey, nil
}
func ToPrivateKey(keyB64 Base64String, auth string) (*ecdsa.PrivateKey, error) {
	keyjson, err := ToBytes(keyB64)
	if err != nil {
		return nil, err
	}
	key, err := keystore.DecryptKey(keyjson, auth)
	if err != nil {
		return nil, err
	}
	return key.PrivateKey, nil
}
// ToPrivateKey returns decrypted *ecdsa.PrivateKey from base64 of encrypted keystore.Key.