cwDup is a Duplicity implementation for Windows systems. It is a packaging of Duplicity, Python, GnuPG, librsync, Cygwin and many other related tools to make it a complete and ready-to-use solution for secure online backup.
Duplicity is an encrypted bandwidth-efficient backup solution using the rsync algorithm. Duplicity produces a local encrypted tar archive of a directory, before uploading it to a remote or local storage location. As Duplicity uses librsync, the incremental archives are space efficient and only record the parts of files that have changed since the last backup. Duplicity uses GnuPG to encrypt and/or sign these archives, which will then be safe from spying and/or modification on the server side. GnuPG allows to encrypt and sign your data and communication, features a versatile key management system as well as access modules for all kinds of public key directories. Cygwin is a Linux-like environment for Windows. It consists of a DLL (Cygwin1.dll), which emulates substantial Linux API functionality, and a collection of tools.