I read a lot of messages concerning sorting of documents in order of
their size. What happens with very big files?
As far as I understand now, my client only has contact with a small
number of other clients. This means that whatever file I want to
retrieve, it has to be copied onto my neigbour's computer before it's
sent to me. Of course, these computers have a limited disk storage, so
we want to throw out unpopular data. But there's another problem: what
if the file I want to request is
bigger then the disk storage on the computer it is supposed to pass
trough?
You have to consider splitting big files into smaller blocks. This also
has the potential to improve anonymity ("Divide and conquer"), because
the pieces can be scattered all over the place.
Once you do that, performance could also be improved by routing pieces
of the big file in parallel trough different computers.
You could even add redundancy (a la RAID) to fix loss of a few blocks.
To give an idea how to split big files into smaller chunks, consider the
following scenario:
I have a big file, which I want to admit to freenet.
First, we generate a new PGP key pair to use for this file.
Then, the file is splitted the into blocks of let's say 128 Kb and
encrypted with the PGP key we just generated. Each block gets a unique
identification key not understandable by humans, let's say it's PGP
fingerprint.
All these blocks are then submitted to the freenet. Then, no one has any
idea what is in there. It's just a chunk of encrypted data with a
identification key that doesn't make sense, and you don't have a clue
where the key to decrypt the data can be found.
Now, a 'master' file is created containing all the identification keys
for the blocks and the public key to decrypt the blocks, but there's no
actual data in this 'master' file.
In order to retrieve the whole file, you'd have to get the master file
first, then request it's parts, decrypt them and put them back together.
Now try to trace back where it came from, or try to prove that there's
sensitive data on my freenet drive.
-- Arend Lammertink --
--
"I worry about my child and the Internet all the time, even though she's
too
young to have logged on yet. Here's what I worry about. I worry that 10
or 15
years from now, she will come to me and say 'Daddy, where were you when
they
took freedom of the press away from the Internet?' " -Mike Godwin
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