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Re: Strong hashing/ciphers for LUKS; was "Encrypting an External HDD"



Hi all,

After I sent the post below, I stumbled upon the cryptsetup FAQ
page[1]. It answered a lot of my concerns, including the SHA1 and the
cipher (plain, plain64, xts, essiv) issues.

[1]
https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions

Thanks!

On Thu, 16 Apr 2015 15:07:25 -0400
Stephen R Guglielmo <srguglielmo@gmail.com> wrote:
> Thanks for all the replies in the previous thread! I've been doing
> some reading and have another question. It seems the default for LUKS
> (as displayed by `cryptsetup --help`) is:
> 
> aes-xts-plain64, Key: 256 bits
> LUKS header hashing: sha1
> RNG: /dev/urandom
> 
> I would like to have a high level of security. Can I use /dev/random
> instead of /dev/urandom to have a more cryptographically-secure RNG?
> Or will I run out of entropy and start blocking? Is the RNG used for
> everyday use of the encrypted volume, or just the initial format? If
> the latter, I can deal with some blocking as I generate additional
> entropy.
> 
> I checked /proc/crypto, and I don't see anything "stronger" than sha1.
> sha1 was beginning to be considered insecure in roughly 2005. Can I
> somehow get support for sha512?
> 
> As for the cipher, I'm not too familiar on such things. cryptsetup(8)
> says I can "optionally set a key size of 512 bits with the -s option."
> I do see options in /proc/crypto about "xts-aes-aesni". Would this be
> faster/better since it's using the AESNI instruction set on my CPU?
> 
> I have a (never-expiring) paste of my /proc/crypto at
> https://paste.debian.net/167171/
> 
> Thank you all!

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