[geeks] Cheap/reliable backup?

[Mouse]

> One thing is for sure, incremental backups based on an encrypted
> whole-drive don't make sense.

Sure they do.  You just need to use a random-access encryption system.
A number of them have been designed, most of them specifically for disk
encryption AIUI.  (At its simplest, consider a block cipher whose block
size equals your disk sector size, used in ECB mode.  You likely don't
want to actually use something that simple, because it has a number of
issues - to pick two of the most obvious, it's vulnerable to
replay/rollback attacks, and when two sectors are identical it leaks
the fact that they are.)

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