duplicity - Encrypted bandwidth-efficient backup using rsync algorithm

Duplicity backs up directories by producing encrypted tar-format
volumes and uploading them to a remote or local file server. Because
duplicity uses librsync, the incremental archives are space efficient
and only record the parts of files that have changed since the last
backup. Because duplicity uses GnuPG to encrypt and/or sign these
archives, they will be safe from spying and/or modification by the
server.