Incremental encrypted backup on DVDs or similar media?

Hi,

I am looking for a solution to the following problem:
A big amount of data needs to be backed up regularly on external media
such as DVD-RAM or MO disks; external hard disk drives are already
used for secondary backup but this is required in addition.

TrueCrypt works well with hard disks and therefore can be used for
encrypted backups onto these. However, TrueCrypt does not work well at
all with external media such as DVD-RAM or MO disks, it is slow as
hell (writing into a TrueCrypt container on a DVD-RAM is maybe 50x
slower than normal writing onto a DVD-RAM).

Since only a small fraction of the data changes from time to time,
incremental (or differential) backups are performed.

Now, I haven't found a pratical solution yet to save incremental
backups onto external media like DVDs in an encrypted form.
1) TrueCrypt is not an option for the above named reason.
2) Creating one single encrypted ZIP, RAR or any other compressed
archive is not an option because it would require rewriting that huge
file every time a backup is made. The same applies to creating a disk
image. BTW, is there any disk imaging software that can reliably
perform incremental (or differential) backups that are encrypted with
a *secure* algorithm like AES (a simple password is not enough)?
3) There are tools that encrypt each file individually. In this case,
one huge file wouldn't have to be rewritten every time a backup is
made. But then how can I automatically detect AND select those
modified or new files for encryption and backup?

Do you know any solution for creating incremental encrypted backups on
DVDs or similar media?

Peter

Previously Peter Frank wrote:
Hi,

I am looking for a solution to the following problem:
A big amount of data needs to be backed up regularly on external media
such as DVD-RAM or MO disks; external hard disk drives are already
used for secondary backup but this is required in addition.

TrueCrypt works well with hard disks and therefore can be used for
encrypted backups onto these. However, TrueCrypt does not work well at
all with external media such as DVD-RAM or MO disks, it is slow as
hell (writing into a TrueCrypt container on a DVD-RAM is maybe 50x
slower than normal writing onto a DVD-RAM).

Since only a small fraction of the data changes from time to time,
incremental (or differential) backups are performed.

Now, I haven't found a pratical solution yet to save incremental
backups onto external media like DVDs in an encrypted form.
1) TrueCrypt is not an option for the above named reason.
2) Creating one single encrypted ZIP, RAR or any other compressed
archive is not an option because it would require rewriting that huge
file every time a backup is made. The same applies to creating a disk
image. BTW, is there any disk imaging software that can reliably
perform incremental (or differential) backups that are encrypted with
a *secure* algorithm like AES (a simple password is not enough)?

Use Gnu tar. It does incremental by timestamp. For this it uses
a file with the last backed up time for each file and backs
up only if the file on disk is newer. Only the file with the
timestamp needs to be unencrypted. For encryption you can then use
GNUpg/PGP.

3) There are tools that encrypt each file individually. In this case,
one huge file wouldn't have to be rewritten every time a backup is
made. But then how can I automatically detect AND select those
modified or new files for encryption and backup?

As I said, GNU tar does it for you. I believe there is a port
for Windows as well.

Do you know any solution for creating incremental encrypted backups on
DVDs or similar media?

See above. With this approach only the archives would be encrypted,
the disk itself would be unencrypted.

Arno