Re: [Question] Distinction responsibilities LUKS and dm-crypt

[Arno Wagner <arno@wagner.name>]

First, dm-crypt is the base-mechanism on block-layer.
There is a "plain dm-crypt" encryption mechanism in 
cryptsetup, sometimes abbreviated as "dm-crypt". 
This ione comes with no meta-data. You enter a paword
and if you do not use the default parameters, you state 
them as well each time you open the device.

LUKS adds a header with metadata, possibilities to use
more passwords and use non-default settings withouth
having to state them each time. But LUKS basically only
does a more elaborate set-up and then passes the actual
work on to dm-crypt. 

I hope that clears up some of the confusuion.

Regards,
Arno




On Thu, Mar 31, 2022 at 20:21:00 CEST, Surmont Jasper wrote:
> Dear, keep in mind I’m fairly new to Linux kernel development and
> similar, so my question might sound stupid. 
>  
> Reading through the documentation of both dm-crypt and LUKS, 
> I understand that LUKS is a format specification 
> to allow FDE, and that dm-crypt is a dm target which allows
> encryption / decryption of writes / reads to the block device. 
> 
> However, I'm unsure about
> what each of these now exactly provides (ie what are the responsibilities). In
> the slides  (look link at the bottom) that the author (Milan Broz) made,
> it mentions that LUKS2 can also provide integrity protection (hence making the
> encryption authenticated). From this, and also reading the Luks1 specification
> I think this is not possible in LUKS1. However, later in the slides it talks
> how dm-crypt allows for authenticated encryption. This is where I'm confused;
> do we assume we use LUKS2? 
> 
> I feel like I'm not really grasping the main function and responsibilities of both LUKS and dm-crypt. 
> Thanks! 
>  
> Slides: https://archive.fosdem.org/2018/schedule/event/cryptsetup/attachments/slides/2506/export/events/attachments/cryptsetup/slides/2506/fosdem18_cryptsetup_aead.pdf 
>  
> Sincerely, Jasper Surmont  

-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno@wagner.name
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