Messages in this thread | | | Date | Fri, 13 Oct 2000 22:15:21 +0000 | From | Marc Mutz <> | Subject | Re: A patch to loop.c for better cryption support |
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Andi Kleen wrote: > > On Fri, Oct 13, 2000 at 05:04:08PM +0000, Marc Mutz wrote: > > Andi Kleen wrote: > > > > > <snip> > > > 2.4 has already broken backwards compatibility to 2.2 (IV changed > > > from disk absolute to relative). When you change it now (before 2.4.0) > > > it is relatively painless. I think the change is a good idea. > > <snip> > > > > You're wrong. All kernels from int-2.2.10.4 onwards can be configured to > > use relative block numbers as IV's. Both the FAQ in Documentation/crypto > > and my HOWTO suggest to set CONFIG_BLK_DEV_LOOP_USE_REL_BLOCK to 'y'. > > That is not a standard kernel option. I'm not talking about any unofficial > patchkits like the i* patches, just about what the standard loop device does. > An encryption module can be backwards compatible itself by mapping the blocks > itself, but without changes it will have an incompatible on disk format. >
This thread was about encryption. And it was about IV's. The only encryption that vanilla loop.c (from 2.2.17) offers is 'none' and 'xor'. None is just that: a no-op. And xor does not use an IV. So the only ciphers that could possibly have been adressed by this patch are the ones in the kerneli patch. So the on-disk format did _not_ change between recent int-2.2.x.y kernels and 2.4-testx, provided the user followed the recommendations and used the previously mentioned option to use relative block numbers as IV's.
Marc
-- Marc Mutz <Marc@Mutz.com> http://EncryptionHOWTO.sourceforge.net/ University of Bielefeld, Dep. of Mathematics / Dep. of Physics
PGP-keyID's: 0xd46ce9ab (RSA), 0x7ae55b9e (DSS/DH)
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