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From: Fourhundred Thecat <400thecat@gmx.ch>
To: Milan Broz <gmazyland@gmail.com>, dm-crypt@saout.de
Subject: Re: [dm-crypt] detached LUKS header size
Date: Mon, 25 Nov 2019 16:17:07 +0100	[thread overview]
Message-ID: <5DDBF073.1050409@gmx.ch> (raw)
In-Reply-To: <4c3b11fc-783c-e58f-681d-7acee12376d7@gmail.com>

> On 2019-11-25 14:55, Milan Broz wrote:

Hi Milan,

just to make sure there is no misunderstanding:

> Then there is alignment, so the real data offset is aligned by default to
> the 1MB boundary.
>
> With this padding, header size is for 128bit key 2MB, for 256/512 key 4MB.

I am actually using 512 bit key:

 --cipher aes-xts-plain64 --key-size 512 --hash sha512

so it would seem I need 4MB header for luks1 with 512 key

> Yes. For reference: for 128bit it is 528384 bytes, for 256bit 1052672
> bytes,
> for 512bit (2x256bits in XTS mode) it is 2068480 bytes.

now I am confused. 2068480 is less than 2MB. So when aligned to 1MB
boundary, 2MB would be enough for luks1 with 512 key.

So is it 2MB or 4MB ?

many thanks,

  reply	other threads:[~2019-11-25 15:17 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-23  5:43 [dm-crypt] detached LUKS header size Fourhundred Thecat
2019-11-23  8:21 ` Arno Wagner
2019-11-24  6:34   ` Fourhundred Thecat
2019-11-24  8:16     ` Arno Wagner
2019-11-24  8:39       ` Milan Broz
2019-11-23  8:48 ` Milan Broz
2019-11-25  4:34   ` Fourhundred Thecat
2019-11-25 13:55     ` Milan Broz
2019-11-25 15:17       ` Fourhundred Thecat [this message]
2019-11-25 15:27         ` Milan Broz
2019-11-24 11:46 ` Michael Kjörling

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