Hi,
 Installing latest version (tested on 2 arch : x32 and x64 on windows
7 pro SP1), with just openssh and openssl installed,

running cygwin shell as an administrator :
passwd -R
 leads to
Storing password failed: Function not implemented
There was a previous post about this :
http://cygwin.com/ml/cygwin/2014-02/msg00471.html

Like suggested there I tested on cygwin < 1.7.28-2 and the password is
correctly saved.

Best regards,
Sébastien