Is It possible to move or transfer an encrypted iPhone backup between computers?
Definitely! The iPhone backups are stored in your user account's app data section.


Open Finder, and select the “Go” menu at the top of the screen. Hold the Option key, and select the “Library” menu option from the Go menu. (On OSX Lion and above, Library will only appear with the Option key held.)
From Library, navigate to Application Support -> MobileSync -> Backup.


(In iTunes preferences -> Devices, you can also right-click on the backup and select Show in Finder on Mac.)

In here, your backups are folders named with the device id for the iPhone (and a date after it sometimes). Make sure you grab the whole folder, and put the folder in on the new computer in the Backup folder there. You can make the folders if iTunes hasn't yet. 

Here's a blog post I wrote about it on Mac and Windows, and matching up the UDID to your iPhone.
https://deciphertools.com/blog/where-are-iphone-backups/