Custody Verification in XRP

[Debasish]

Custody Verification of an XRP Address :

I have an Xrp Address , public key , private key , message and signed message .(created all of these using test net)

To identify owner of any particular address we have the first approach but i want to achieve the same using second approach.

1. we can ask xrp address owner can do a transaction to some account to validate that they are the actual owner of that address - 

2. Using Public key , signed message and message - how to custody verify an xrp address.