So, what will we get from your signature message ?
Proof of account ownership...I will sign an old address from an old transaction here:
Bitcoin signed message
-----BEGIN BITCOIN SIGNED MESSAGE-----
meatmeat Nov 15 2017 account owner
-----BEGIN BITCOIN SIGNATURE-----
Version: Bitcoin-qt (1.0)
Address: 1MqogTNJBekPFqYQtZFHqqwLfZoXGJTJpL
IKlSjdSjG++Fx/hd/ESS/rdhUtI8hLRkOu4Wor3AXeLVaTy2qR6aPxyWWGvYy813+MlSSuYZtwykaXRxpWov7mc=
-----END BITCOIN SIGNATURE-----
address used here in previous loans:
https://bitcointalk.org/index.php?topic=1846463.0