[dm-crypt] LUKS overhead?

Ralf Ramsauer ralf+dm at ramses-pyramidenbau.de
Tue Sep 9 19:32:02 CEST 2014

Hi Ryan,

On 09/09/14 18:11, Ryan Nix wrote:
> Can anyone tell me if we'll see the same kind of increases in file
> size?  I ask because we're trying to plan on how much storage we
> should buy.

There will be no increase of the size of 'files'.
Luks resp. dm-crypt is just a layer between block devices and actual
So the actual size of files depends on your filesystem and not on luks
or dm-crypt.

Dm-crypt uses blockciphers. In short words that means that x byte
plaintext will be encrypted to x byte ciphertext, without any overhead
or increase of size.

I don't know how owncloud's stock encryption solution exactly works, but
are you sure, that Luks does really satisfy your requirements?
All files of all users will be encrypted with the same key when using
Luks and when your filesystem is mounted, the webserver process or other
processes may have access to all files, regardless of encryption.


Ralf Ramsauer
GPG: 0x8F10049B

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