Warning! New cryptographic modes!

[silky]

How about this.

When you modify a file, the backup system attempts to see if it can
summarise your modifications into a file that is, say, less then 50%
of the file size.

So if you modify a 10kb text file and change only the first word, it
will encrypt that component (the word you changed) on it's own, and
upload that seperate to the file. On the other end, it will have a
system to merging these changes when a file is "decrypted". It will
actually be prepared and decrypted (so all operations of this nature
must be done *within* the system).

Then, when it reaches a critical point in file changes, it can just
upload the entire file new again, and replace it's "base" copy and all
the "parts".

Slightly more difficult with binary files where the changes are spread
out over the file, but if these changes can still be "summarised"
relatively trivially, it should work.

--
silky

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