Re: Best mode of operation for AES-128 on x86_64?

[Zdenek Kaspar <zkaspar82@gmail.com>]

Dne 13.5.2010 2:07, Pedro Ribeiro napsal(a):
> Hello,
> 
> I'm currently using a LUKS volume which contains an encrypted LVM with
> itself contains my root, home and swap partitions.
> 
> My processor is a core 2 duo 2.26ghz and I'm running x86_64. I'm using
> cbc-essiv:sha256 and AES with 128 bit key.
> 
> I was wondering, is CBC mode the fastest?
> I have a fast processor and can't really complain about the read/write
> speed, but I was wondering if I could gain any speed from counter mode
> or other mode.
> 
> I would also like to ask what are the real world speed gains when
> using AES-NI? Can anyone please point me to some benchmarks, if there
> are any?
> 
> Thank for the help,
> Pedro

Hi Pedro, you can get better speeds with lower security. But before you
change your working scheme (which is good imo, I prefer XTS..) do a
quick test and compare if it's worth the pain :) ie:

$ hdparm -t /dev/sda1
$ hdparm -t /dev/mapper/sda1_crypt

Here are some numbers you should check -
http://blog.wpkg.org/2009/04/23/cipher-benchmark-for-dm-crypt-luks

My guess for single drive you're fine with your setup..

>From measuring specific server-loads and the impact on CPU frequency
scaling with cpufreq-ondemand as governor I would recommend lowering
default threshold value (95) for this load on desktop/server. ie:

$ echo 50 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold

HTH, Z.