From: Felix Rubio <felix@kngnt.org>
To: dm-crypt@saout.de
Subject: Re: [dm-crypt] length of keyfiles
Date: Wed, 06 Jan 2021 12:08:47 +0100 [thread overview]
Message-ID: <3674619b2202e99b31fac7043e6edba5@kngnt.org> (raw)
In-Reply-To: <20210106104746.GA3386@tansi.org>
Thank you for your answer Arno... and for confirming that I should
finally get rid of those double density floppy disks and reader :-P
Regards!
Felix
---
Felix Rubio
"Don't believe what you're told. Double check."
On 2021-01-06 11:47, Arno Wagner wrote:
> Hi Felix,
>
> I assume we are talking LUKS here, plain mode is different.
>
> The longer length is both convenience and helps if you
> use low-entropy input. The keyfile does not actually
> hold a key (LUKS mode), but a passphrase. Passphrases
> get hashed, and once you have maximum entropy, you
> cannot get more. I would need to look up what length
> is actually used, but it does not depend on the lenght
> of the encryption key. That one is stored in the anti-forensic
> stripes, protected with the hash from that passphrase.
>
> So, to make this short, if you use LUKS with a keyfile,
> putting in more entropy than used is meaningless.
> If your random data is from /dev/random or (properly
> initialized) /dev/urandom, 64 bytes are more than enough.
>
> Also, the differences between an 8kB passphrase and a
> 64B one in execution time should not be noticeable at all.
> Unless you read it from floppy disk ;-)
>
> Regards,
> Arno
>
>
> On Wed, Jan 06, 2021 at 10:17:22 CET, Felix Rubio wrote:
>> Hi everybody,
>>
>> I have seen that keyfiles can be used in cryptsetup up to 8 kB, but
>> internally the master key is 512 bits at max. Is there any
>> recommendation
>> / increased security by using a random sequence of 8 kB w.r.t., let's
>> say,
>> one of just 64 bytes?
>>
>> I understand that using one of 8kB will require more time than one of
>> 64 B
>> when unlocking the volume, but... is the former really that much more
>> secure than the latter?
>>
>> Regards!
>> Felix
>> _______________________________________________
>> dm-crypt mailing list
>> dm-crypt@saout.de
>> https://www.saout.de/mailman/listinfo/dm-crypt
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next prev parent reply other threads:[~2021-01-06 11:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-06 9:17 [dm-crypt] length of keyfiles Felix Rubio
2021-01-06 10:47 ` Arno Wagner
2021-01-06 11:08 ` Felix Rubio [this message]
2021-01-06 11:17 ` Felix Rubio
2021-01-06 14:06 ` Arno Wagner
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