Read Introduction To Algorithms and get the MIT open courseware for
the book from their site or iTunes Univ.
At least you get a start that way
Sam
On Feb 15, 2008, at 6:08 PM, Randy Barlow wrote:
[EMAIL PROTECTED] wrote:
I spent time about a year ago looking into good encryption. At that
time, cryptsetup was the best bet. Its really easy to use. With
cryptsetup, your best off encrypting an entire filesystem/partition
so
there are no restrictions regarding size.
As far as ciphers, there are three popular ones that are 256 bits
in the
Linux kernel. You'll have to pick the one(s) you like best.
Generally,
everyone agrees Serpent is the strongest, followed by AES then
followed
by TwoFish. From my tests, performance of the algorithms is in
reverse
order (meaning TwoFish is the fastest). Linux is a bit behind last I
checked regarding encription modes of operation and seems to only
offer
ECB or CBC. CBC is Chain Block Cipher and is based on an IV which is
like an index into your media. The IV is used to encript a block of
data so a previous identical block wont be identically encrypted. As
far as your question regarding one-bit changes, a one bit change will
have the effect you mentioned but only for one encrypted block.
I'd recommend reading up on the ciphers to see what you like.
There has
been some talk about TwoFish being broken however I find it hard to
believe. There has been a lot of talk about TrueCrypt on Linux.
From
what I can tell, it seems a bit more advanced and supports different
(more modern?) modes of encryption.
Thanks for the reply Brian! In a course I am taking this semester, we
have learned the nitty gritty of AES, and I think I am pretty happy
with
that one given a long enough key (256 is way plenty!) I have been
playing around with the creation of the file for the loopback block
device for dm-crypt, and I have learned some surprising things about
filesystems. Can anybody explain the following to me?
If I create a file like this:
dd if=/dev/zero bs=1000000000 of=/path/to/crytped/file
it makes a file that takes up 1 GB of hard drive space. It takes a
while to write to disk, and you will notice that the file is 1 GB with
ls -l and you will also notice a change in the space for the partition
using df.
If I create a file like this:
dd bs=1 seek=1GB if=/dev/null of=/path/to/crypted/file
it makes a file that reports itself to be 1 GB long by ls -l, but
doesn't seem to write 1 GB to the disk. Also, df doesn't report 1 GB
less than before you run the command.
What's happening here? I had assumed before I did this that the
output
of ls -l is the actual number of bits consumed by a file, but that
doesn't seem to be the case anymore.
I created a file using the second command, and now as I copy files
into
it I can see the disk space going down bit by bit. This is really
what
I wanted in the first place, but I am just confused as to what is
really
going on. Could anybody explain, please?
--
Randy Barlow
http://electronsweatshop.com
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