Strong encryption

Donovan Baarda abo at
Wed Jun 5 21:42:02 EST 2002

On Wed, Jun 05, 2002 at 03:33:23AM -0700, 'jw schultz' wrote:
> On Wed, Jun 05, 2002 at 12:21:18PM +0200, C.Zimmermann wrote:
> > > 
> > > If you want them stored on the destination encrypted you
> > 
> > Yes, that?s it. The owner of the source files will be sure, that no one
> > else can read his files on the destination host.
> > 
> > I thought, rsync only looks at the modification date of a file and
> > decides whether to backup this file or not. In this case, the backup
> > could be stored  encrypted.
> Rsync can handle encrypted files just fine.  It just treats
> them as ordinary binary files.  If the owner of the files
> encrypts them on the source they will be encrypted on the
> destination.
> As you have said rsync normally just looks at the
> modification date for deciding whether to update the
> destination (unless you use the -c option)  But, unless the
> -w option is used rsync will use some rather clever (nod to
> rsync developers) methods to transfer only the changed the
> parts of changed files.  It is this feature that gives rsync
> its speed.  My comments below are to advise you that that
> clever feature is nullified by encrypted files.  In fact for
> encrypted files rsync would be sub-optimal.  If most/all of
> the changed files are encrypted i would use the -w option.

Perhaps he wants a gpg-rsyncable patch to gpg?

Seriously, such a thing would be possible. After the long thread in which I
made a dick of myself discussing how gzip-rsyncable couldn't possibly work,
only to have someone explain how it does, I now know how it could be done;
encript the data in chunks, where the chunk boundaries are determined by the
same heuristic gzip-rsyncable uses.

I think I could even whip up a working Python wrapper around gpg in a day or
so that could do the job... but I'm too buisy looking for paid work right
now to do it so I'll leave it as an excersise for others :-)

ABO: finger abo at for more info, including pgp key

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