[dm-crypt] Block size and tweak value

Arno Wagner arno at wagner.name
Fri Jun 10 18:01:42 CEST 2016


the block size is always 512 bytes for cryptsetup. The 
tweak is, I think, the block-number as counted from the 

You can read the key and offset as described in FAQ Item 6.10.


On Fri, Jun 10, 2016 at 17:02:52 CEST, jonetsu wrote:
> I would like to determine the block size that's used with aes-xts-plain64 as well as the tweak value. The file system is ext2 and the information returned by parted is:
> Model: Linux device-mapper (linear) (dm)
> Disk /dev/mapper/luksvg-confd: 21.0MB
> Sector size (logical/physical): 512B/512B
> Partition Table: loop
> Number  Start  End     Size    File system  Flags
>  1      0.00B  21.0MB  21.0MB  ext2
> The command used is:
>   cat /root/cryptkey | cryptsetup luksFormat /var/lib/luksfile --key-file - --cipher aes-xts-plain64 \
>   --key-size 256 --hash sha512 -i 5000 --align-payload 2048
> How can the value of the block size and the tweak value ne known ?
> Thanks.
> _______________________________________________
> dm-crypt mailing list
> dm-crypt at saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt

Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
A good decision is based on knowledge and not on numbers. -- Plato

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier

More information about the dm-crypt mailing list