FYI, users of cwRsync might be interested in this project:
which provides an rsync compatible encryption and compression algorithm. (At least in theory. I haven't got it working yet.)
I ran across it while looking for a Win32 binary of gzip that had been patched to include an rsync compatible algorithm.
In case you were wondering, you can't use any old form of compression and expect rsync to be able to work efficiently (transfer only the chunks of files that changed), because as explained here:
due to the way the compression algorithms work, if you change one part of the source file, it tends to alter the entire compressed file, resulting in it having little resemblance to the prior version.
The same is also true for encryption. So people have developed algorithms that are constrained to operate within fixed blocks, so a change in one block doesn't alter other blocks of the file.
rsyncrypto seems to be at an early stage and still rather rough, but it would be good to see it bundled with cwRsync at some point. If nothing else, including the patched gzip binary would be helpful.
It seems interesting. Many rsync users can benefit from rsyncable gzip. It seems that this patch existed for a while. I need to confirm that there exists a patch that can be used on gzip version packaged in cwrsync. Still investigating ...