Hi Shachar,
I have a couple of queries regarding Windows usage:
1) when I compile rsyncrypto-0.18 with cygwin, the resulting executable is much larger (1.11Mb)... I'm not sure if this is normal.
I also realised that this executable is around 7 times slower (both running simply on windows command line, not cygwin) than the precompiled rsyncrypto-0.18 as downloaded from the site. Maybe this can be a clue as to where the Win performance loss might be?
 
2) When encrypting with the symmetric key, is AES128 or 256 used?
 
Thanks
Julian