How to add a passphrase on the OpenVPN client cert

[albertredneck]

Title says it all.

I've followed the multiple internet tutorials to setup OpenVPN server sin TrueNAS.

It worked wonderfully, but the exported client key doesn't have a passphrase so it feels a bit "unprotected". I've reviewed both the certificate creation form and the OpenVPN Server settings in TrueNAS and I cannot find anything that looks like what I'm looking for.

I'm very noob with OpenVPN and all this certificates thing (I don't even know if what I'm asking makes sense at all!), so I'd appreciate any help. Thanks!