verifySign method
Verify if the given signature is valid for the given message or text document, based on given keypair
Implementation
bool verifySign(String document, String signature) {
SignatureBase fomartedSignature = Signature(base64Decode(signature));
return rootKey.verifyKey.verify(
signature: fomartedSignature,
message: document.codeUnits.toUint8List());
}