[dm-crypt] Key-Slot Checker Tool
arno at wagner.name
Sun Sep 9 23:40:09 CEST 2012
On Sun, Sep 09, 2012 at 03:35:12PM +0200, Arno Wagner wrote:
> On Sun, Sep 09, 2012 at 10:27:44AM +0200, Milan Broz wrote:
> > (And the same random test perhaps should be in tests for large
> > enough blocks - see tests/differ.c, there is nice fixme :-)
> Will have a look.
Question for that, is the "R" option one random thing
replaced with another random thing? If so, I can fix
that test by XORing both and calculating entropy on the
Will still require -lm for the log() though.
And an update on the 0.85 threshold: I have checked 10 Million
random 512B blocks and the sample entroy never went below 0.92.
For larger blocks the probability will be even lower. I think
0.85 is quite adequate as threshold.
However, the test in differ.c will probably need to go
back to a count of differing bits for blocks significantly
smaller than 512B or use a lower threshold. Is it used for
small blocks, e.g. keys?
> > I am just not sure introducing floating point in libcryptsetup
> > is good idea.
> While this can be done without, it is really hard. Basically
> you eiher need to simulate the logarithm in fixed-point integer
> or build up huffman tree as direct entropy estimator. Easiest way
> would probably be fixed-point and a 1000-entry table for the
> > But perhaps this can be compile time option,
> > if some ancient/embedded CPU/distro has problems here,
> > so it can be compiled-out.
> I like that idea much better.
> So, next step, make it use luks.h and put it in misc/ ?
> Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno at wagner.name
> GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
> One of the painful things about our time is that those who feel certainty
> are stupid, and those with any imagination and understanding are filled
> with doubt and indecision. -- Bertrand Russell
> dm-crypt mailing list
> dm-crypt at saout.de
Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno at wagner.name
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
One of the painful things about our time is that those who feel certainty
are stupid, and those with any imagination and understanding are filled
with doubt and indecision. -- Bertrand Russell
More information about the dm-crypt