Re: loop.c transfer module api
kernel@draper.net
Tue, 7 Sep 1999 09:10:25 -0500
On Tue, Sep 07, 1999 at 03:50:41PM +0200, Alexander S A Kjeldaas wrote:
> On Tue, Sep 07, 1999 at 07:20:03AM -0500, kernel@draper.net wrote:
> >
> > I think your #2 idea is perfect. Suppose one were to develop a
> > "filesystem signature" in losetup as a hash of the fully qualified
> > device/file name, stuff that into the loop_device structure, and then have
> > loop.c pass IV = relative_block + signature into the transfer module.
> > The result is both relocatable and avoids duplication of ciphertext...
> > the best of both worlds.
> >
>
> The IV should be _random_, not secret. Just look at the operation of
> CBC mode. Each block of ciphertext is the next block's "IV". So
> there is no reason to keep the first IV secret when all the other
> "IVs" are exposed. What we want to do is to keep the first IV
> _random_.
>
You do not consider a hash of the device/file name to be sufficiently
random?
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