Master - Slave - Galera cluster

The current setup is comprised of two nodes, a Master-Slave setup. No encryption, no compression. I would love to switch this to a Galera Cluster, with encryption, compression and, to make things spicy, no downtime. I was able to insert the Slave into the cluster, and make the other nodes sync from it. The only issue is that, even though I have set the cluster nodes to use encryption and compression, this is not happening. My money on why this isn't working is that the sync is performed via SST - file are being transferred - while in order to enable encryption and compression, I'd either need to import a mysqldump (downtime, so no go), or somehow force an IST. So this is the question: is there a way to force an IST on a new node (no data)? Or, if anyone got any other ideas on making this happen, I'm willing to try it. Thank you.