Ecdsa/Secp256k1
import 'package:secp256k1_ecdsa/secp256k1_ecdsa.dart';
final message = Utilities.hexToBytes('some message here to sign it');
final privateKey = PrivateKey.fromHex('your private key hex');
final signature = privateKey.sign(message);
final publicKey = privateKey.getPublicKey();
final verified = publicKey.verify(signature, message);