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



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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