[lkml]   [2018]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH v2 00/12] crypto: Adiantum support
On 16/11/2018 22:52, Eric Biggers wrote:
> Hi Milan,
> On Sat, Oct 20, 2018 at 12:26:20PM +0200, Milan Broz wrote:
>> Adiantum (as in your current git branches on can be used for dm-crypt
>> without any changes (yes, I played with it :) and with some easy tricks directly
>> through cryptsetup/LUKS as well.
>> I think we should have this as an alternative to length-preserving wide-block
>> cipher modes for FDE.
> Yes, dm-crypt can use Adiantum by specifying the cipher as
> "capi:adiantum(xchacha12,aes)-plain64".
> But, I'm having trouble getting cryptsetup/LUKS to use Adiantum.
> Using LUKS1, the following works:
> cryptsetup luksFormat /dev/$partition --cipher='capi:adiantum(xchacha12,aes)-plain64' --key-size 256
> However, when possible we'd like people to use 4K sectors for better
> performance, which I understand requires using the LUKS2 format along with
> cryptsetup v2.0.0+ and Linux v4.12+. But the following does *not* work:
> cryptsetup luksFormat /dev/$partition --cipher='capi:adiantum(xchacha12,aes)-plain64' --key-size 256 --type luks2 --sector-size 4096

Hi Eric,

actually I planned to test it and then reply to these patches with example cryptsetup
commands, but did not have time for it yet.
So thanks for a reminder ;-)

Recent cryptsetup supports sector-size even for plain device.

You actually do not need to use capi: prefix, Adiantum is a composition,
so "xchacha20,aes-adiantum-plain64" works as well (and it should work even for old cryptsetup).
(It is ugly, but it should be compatible.)

# cryptsetup open --type plain -c xchacha20,aes-adiantum-plain64 -s 256 --sector-size 4096 /dev/sdb test

For LUKS and benchmark, Adiantum need to use 32 bytes IV. And we have these parameter,
unfortunately, hardcoded...
(I guess there is already a way how to get this dynamically from userspace crypto API now.)

So, I already added patch to devel branch patch for benchmark to support Adiantum few days ago

This allows trivial benchmark (but it just encrypts one big blob of data):

# cryptsetup benchmark -c xchacha20,aes-adiantum -s 256
# Tests are approximate using memory only (no storage IO).
# Algorithm | Key | Encryption | Decryption
xchacha20,aes-adiantum 256b 146.6 MiB/s 148.0 MiB/s

# ./cryptsetup benchmark -c xchacha12,aes-adiantum -s 256
xchacha12,aes-adiantum 256b 181.7 MiB/s 184.6 MiB/s

For LUKS2, we need a similar change to cryptoAPI IV size (unfortunately it does not
fallback to old keyslot handling, so LUKS2 does not work currently now).

I quickly added a workaround that fallbacks to default keyslot encryption for keyslots
in this case

then you can use LUKS2
# cryptsetup luksFormat --type luks2 --sector-size 4096 -c xchacha20,aes-adiantum-plain64 -s 256 /dev/sdb

(Example above will encrypt keyslots with AES-XTS and use Aviantum for data only.)

So, unfortunately yes, we need some small changes in cryptsetup for LUKS;
plain mode should work out of the box (with the syntax above).


 \ /
  Last update: 2018-11-17 11:30    [W:0.100 / U:0.924 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site