sign method
Signs a blob of data, with this identity's private key. @param challenge - challenge to sign with this identity's secretKey, producing a signature
Implementation
@override
Future<BinaryBlob> sign(dynamic challenge) {
final blob = challenge is BinaryBlob
? challenge
: blobFromBuffer(challenge as ByteBuffer);
return Future.value(_sk.sign(blob).signature.asTypedList);
}