On Mon, Oct 28 2013 at 6:21pm -0400, Milan Broz <gmazyland@xxxxxxxxx> wrote: > The dmcrypt already can activate TCRYPT (TrueCrypt compatible) > containers in LRW or XTS block encryption mode. > > TCRYPT containers prior to version 4.1 used CBC mode with some > additional tweaks. > > This patch adds support for these containers. > > The mode is implemented using special IV generator named TCW > (TrueCrypt IV with whitening). > > TCW IV supports only containers encrypted with one cipher > (Tested with AES, Twofish, Serpent, CAST5 and TripleDES). > > While this mode is legacy and is known to be vulnerable > to some watermarking attacks (e.g. revealing of hidden disk > existence) it can be still useful to mount old containers > without using 3rd party software or for independent forensic > analysis of such containers. > > (Both userspace and kernel code is independent implementation > based on format documentation and completely avoids use of original > source code.) > > The TCW IV generator uses two additional keys, Kw (whitening > seed, size is always 16 bytes - TCW_WHITENING_SIZE) and > Kiv (IV seed, size is always of the IV size of selected cipher). > These keys are concatenated to main encryption key in mapping table. > > While whitening is completely independent from IV, it is > implemented inside IV generator for simplification. > > Whitening value is always 16 bytes long and is calculated > per sector from provided Kw as initial seed, xored with > sector number and mixed with CRC32 algorithm. > Resulting value is xored with ciphertext sector content. > > IV is calculated from provided Kiv as initial seed and > xored with sector number. > > Detailed calculation is in Truecrypt documentation for version < 4.1 > and will be also described on dmcrypt site > http://code.google.com/p/cryptsetup/wiki/DMCrypt > > The experimental support for activation of these containers > is already present in git devel brach of cryptsetup. > > Signed-off-by: Milan Broz <gmazyland@xxxxxxxxx> I pushed this to linux-next (for v3.13), see: https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=8a478f032b40a28a66559a91095d0e0733194389 Tweaked the header and text in dm-crypt.txt and maybe a few other comments. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
