The InTrust Agent registration password is the same as the InTrust Organization password following the installation of InTrust however the InTrust Agent registration password can be changed at any time with no issues/conflicts so it may have been changed at some point in the past. If you cannot determine what the InTrust Agent registration password is it can be reset using the steps below:
1) Open the InTrust Manager snap-in.
2) Expand Configuration | InTrust Servers
3) Right-click on the InTrust server where you are attempting to handshake the InTrust Agent and select 'Properties'
4) Select the 'Agent' tab
5) Enter a new password twice and click 'OK'
6) Try the '-add' (registration) command again on the remote server