sign method
Implementation
SignatureData sign(Uint8List messageHash, Uint8List privateKey, [bool isEthereum = false]) {
final signer = ECDSASigner(null, HMac(SHA256Digest(), 64));
final key = ECPrivateKey(decodeBigIntToUnsigned(privateKey), _ecDomainParams);
signer.init(true, PrivateKeyParameter(key));
var signature = signer.generateSignature(messageHash) as ECSignature;
if(!signature.isNormalized(_ecDomainParams)) {
signature = signature.normalize(_ecDomainParams);
}
return SignatureData(signature.r, signature.s);
}