[NBLUG/talk] Crypt Filesystems

Jacob Appelbaum jake at nblug.org
Wed Jul 26 16:38:09 PDT 2006


Walter Hansen wrote:
>>> Ack. I was going through the example 2 Partition backed loop with gpg
>>> encrypted key file and got "/dev/loop3: No such file or directory" did I
>>> miss something?
>>>
>> Let's get some context here?
>>
>> Can you include what you did to build and install loop-aes? What are the
>> steps that led you to this error?
>>
>> Regards,
>> Jacob
> 
> Sure.
> I used apt-get to install loop-aes-utils and module-assistant (already
> installed)
> I used module-assistant to install loop-aes and aes-ciphers-source
> I had to use the fakesource as it said my source was only headers.
> 
> from there I attemtped to follow these instructions:
> <begin>
> Create 65 random encryption keys and encrypt those keys using gpg. Reading
> from /dev/random may take indefinitely long if kernel's random entropy pool
> is empty. If that happens, do some other work on some other console (use
> keyboard, mouse and disks). Use of gpg encrypted key file depends on
> encrypted swap.
> 
>     head -c 2925 /dev/random | uuencode -m - | head -n 66 | tail -n 65 \
>         | gpg --symmetric -a >/a/usbstick/keyfile.gpg
> 
> Fill the partition with random looking data. "dd" command may take a while
> to execute if partition is large.
> 
>     head -c 15 /dev/urandom | uuencode -m - | head -n 2 | tail -n 1 \
>         | losetup -p 0 -e AES128 /dev/loop3 /dev/hda666
>     dd if=/dev/zero of=/dev/loop3 bs=4k conv=notrunc 2>/dev/null
>     losetup -d /dev/loop3
> <end>
> 
> but on the second head... line entry I get the /dev/loop does not exist.
> On looking I don't have any /dev/loopX, but I do have a /dev/loop/0 which
> I assume must be something else as it doesn't seem to work ethier.
> 


Surely these aren't the commands that you executed right? /dev/hda666 is
unlikely to be a valid block device ;-)

Do you have the loop module loaded? I'm a bit confused by the
/dev/loop/0 can you give me some kernel information? uname -a? etc?

Perhaps come by #nblug on irc?


Regards,
Jacob




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