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Date: Thu, 26 Dec 2019 21:38:40 +0000
From: Michael =?utf-8?B?S2rDtnJsaW5n?= <michael@kjorling.se>
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Subject: Re: [dm-crypt] How to compress LUKS v2 header?
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To: dm-crypt@saout.de

On 26 Dec 2019 20:20 +0000, from jfaracco@br.ibm.com (Julio Cesar Faracco - jfaracco@br.ibm.com):
> I'm using `cryptsetup luksHeaderBackup /dev/sda2 --header-backup-file /tmp/backup.header`
> I used ZIP and GZIP, but I got 0% of reduction of `backup.header`. :-(
> Do you have any suggestions of what algorithm should be used to
> compress this type of file?

Why are you trying to compress the header backup in the first place?

As a general rule, encrypted data (such as the parts of the LUKS
header that aren't already random by design) does not compress well;
if data that has been encrypted can be compressed to any notable
degree, that usually means the encryption is somehow flawed, because
it's leaving patterns in the encrypted data. Properly encrypted data
should look completely random, which means that there's very little,
if anything, for compression utilities to find reducible patterns in.

-- 
Michael Kjörling • https://michael.kjorling.se • michael@kjorling.se
 “Remember when, on the Internet, nobody cared that you were a dog?”