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From: Milan Broz <gmazyland@gmail.com>
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Date: Thu, 12 Nov 2020 10:36:55 +0100
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Subject: Re: [dm-crypt] Encrypting DVD or CDROM from iso
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To: "Carlos E. R." <robin.listas@telefonica.net>, dm-crypt mail list <dm-crypt@saout.de>

On 11/11/2020 20:16, Carlos E. R. wrote:
> On 10/11/2020 17.22, Davide Marchi wrote:
>> Hi to all,
>>
>> I'm wondering how to create a DVD or CDROM encrypted using dm-crypt.
>> I've followed this tutorial, with no luck: 
>> http://www.sourcentral.org/luks/iso9660/
>>
>> and the DVD or cdrom created cannot be activated:
> 
> Hum. I created encrypted DVD years ago with a similar procedure, 
> somewhat simpler. Basically, I created an empty file of the same size as 
> the CD or DVD, mounted it as a loop device, then I encrypted that loop 
> device, and then I formatted the resulting luks device with any 
> filesystem type I wished, typically XFS.
> 
> This, so far, still works.
> 
> Then I just burn that file to DVD.
> 
> The final step is to mount and decipher the DVD - and this step failed, 
> but it was an XFS error if I remember correctly.

You cannot switch block size in XFS - if DVD reports 2k block and XFS
was formatted with 4k block device, it will never work.

This is not a cryptsetup problem but the way how XFS works.

Try to run lsblk -t and compare reported sector size for DVD device and your
original device. If it is the same, it should work even for XFS.

Milan