On Jul 28, 2012 8:53 PM, "Heiko Baums" <lists@baums-on-web.de> wrote:
>
> Am Sat, 28 Jul 2012 19:44:01 +0200
> schrieb Christoph Vigano <mail@cvigano.de>:
>
> > According to crypttab(5):
> > "size=
> > Specifies the key size in bits; see cryptsetup(8) for possible values
> > and the default value of this option."
> >
> > As it is custom in cryptography, key sizes are given in bits, like RSA
> > 4096 which means the key is 512 bytes long.
> >
> > If your former size argument was given in bytes, convert that number
> > to bits and try again.
>
> But you don't want to tell me, that Lennart Poettering also has written
> his own dd. If this was really the case then I definitively would call
> him mad. But if the new systemd-cryptsetup is using dd then size
> wouldn't need to be in bits.
>
> I'll try it anyway.
>
> Heiko

Just read three man page please, it is documented there. From my memory, size is in bits and offset in bytes.

dd is not used. The key is not written to a temporary file, but libcryptsetup reads the relevant portion of the file/device directly.

Tom