[dm-crypt] LUKS & TrueCrypt - Speed Test

Arno Wagner arno at wagner.name
Thu Jul 28 07:11:17 CEST 2011


On Wed, Jul 27, 2011 at 07:18:24PM -0400, Jorge F?bregas wrote:
> Hello everyone,
> 
> Inspired by this old blog post:
> 
> http://movingparts.net/2007/10/26/truecrypt-versus-luks-speed-test/
> 
> ...I decided to perform some tests on my Fedora 14 box.   This is not a
> pro benchmark so be warned :)
> 
> Common Facts for both tests:
> 
> - source & destination filesystems were ext4
> - destination is an external USB drive
> - source data size is 143GB (a folder with lots of files & directories,
> small & large files, regular data...)
> - rsync was used to perform the actual copy
> - I'm using an "encrypted partition " (against an encrypted file)
> - I did a test first with TrueCrypt and then with LUKS
> - Between the above tests, I shut down the machine (to flush filesystem
> cache).
> - my system kernel: 2.6.35.13-92.fc14.i686
> 
> ### TrueCrypt Results ####
> I used AES-256 (XTS operation mode), hash algorithm: ripemd-160 and the
> package was realcrypt-7.0a-1.fc14.i686
> 
> Output of time command after rsync finished:
> 
> real	105m22.211s
> user	28m10.471s
> sys	41m35.319s
> 
> 
> ### DM-Crypt LUKS Results ###
> I used the defaults:  AES-256 (CBC), sha1 for header hashing and the
> package cryptsetup-luks-1.1.3-1.fc14.i686
> 
> Output of time command after rsync finished:
> 
> real	108m55.291s
> user	28m6.534s
> sys	42m53.400s
> 
> 
> As you can see, there's almost a 4 minute difference.  I was expecting
> LUKS to be faster (as dm-crypt is a kernel module) and TrueCrypt runs
> mainly in user space isn't it?  Do you think the cipher operation modes
> (XTS vs CBC) played a role in this difference? Have any of you performed
> a similar test?

There is an old gemran egineering saying:

"wer mist mist mist" 

(along the lines of "Those who measure measure crap")
I think it applies here.

Real-time is tricky. It does not reflect effort invested. If you 
look at the sys itime, you see that the crypto-effort is only about
90 seconds more. Even that is pretty much below the measurement
error. Very likely the differences are due to storage differences
and do not show crypto-speed differences.

I suggest you run both tests at least 3 times and make sure
your storage is significantly faster than the crypto, e.g. 
by doing this between RAM disks or SSD storage. Also a complex
disk access patterhn like rsync is not suitable as it may
have complex interactions with caching and buffering.

Arno
-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
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