Changing servers

[Arthur Chance]

I'm in the process of switching from an ancient and venerable fileserver 
to a more modern, larger one. Given that most of the file systems 
contents will simply be migrated from one to the other (via zfs 
send/recv), am I correct in assuming I can simply transfer the tarsnap 
key and cache from the old server to the new and tarsnap will just keep 
working without suddenly doubling the size of my archives?