I've posted an initial public release of DeltaSCP, 1.1. Here's the link: https://software.seekye.com/deltascp
This is a simple Linux differential copy utility that operates over SSH. I wrote it in 2010, and posted it on SourceForge briefly -- it appears to be gone now -- but never made a proper release of it.
At any rate, this version uses SHA-256 hashes instead of SHA-1 and has some basic versioning in the protocol so I can improve it in the future if I want to.
Mostly this is useful for backing up virtual machine images over the Internet.
Enjoy!
God bless.
James