Re: [PATCH 4/7] fuse: add POSIX file locking support

[Jesper Juhl]

On 19/06/06, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> > How about; on fuse startup, pick some semirandom number, store it
> > somewhere, then do an XOR of the pointer with the saved value to
> > scramble it, when you need to use it, simply XOR it again with the
> > stored value...  Not especially strong, but better than nothing and
> > better than just adding a constant that people can find out from the
> > source
>
> I think Andrew was suggesting a random key for the ADD function.
>
> > (and the scramble value would be differene each time fuse loads, so
> > at a minimum a different scramble key every boot) - also, XOR is a
> > quite fast operation so overhead should be low.
>
> I think XOR might be even weaker than ADD, because from gessing the
> difference between two values (easy) you might be able to guess the
> bits of the key.
>
> I'm actually looking for something stronger than XOR or ADD, but it's

How about using TEA (Tiny Encryption Algorithm), XTEA or XXTEA then?
They are quite simple algorithms, easy to implement and resonably fast
(with TEA being the simplest, but also weakest).
A hell of a lot better than just a simple XOR or ADD and probably more
than sufficient for this purpose.

 http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm
 http://www.simonshepherd.supanet.com/tea.htm
 http://www.ftp.cl.cam.ac.uk/ftp/papers/djw-rmn/djw-rmn-tea.html


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Jesper Juhl <jesper.juhl@xxxxxxxxx>
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