Re: About crypt...
Thu, 21 May 1998 23:58:54 -0400

On 1998-05-21, wrote:

> Anybody knows how can I get a kind of 'crypt file system' to patch on
> kernel?
> I'd like to do this:

> #mount -t crypt /dev/cryptdev /mnt
> enter password:foo
> cript system mounted...

I believe the loop device has hooks to use DES or IDEA encryption. You must
add the DES code yourself; it can't ship with the kernel. If you do this, be
sure to read Solar Designer's recent message to linux-kernel about some
problems with the current DES addons for loop.c (with patches):
This message also has pointers to the DES addons.

There's another option, one that was suggested when someone asked the same
question a month ago (before that thread degenerated into a rant about why US
crypto laws suck). It may be a bit clunky, but TCFS can do this. TCFS =
Transparent Cryptographic FileSystem. IIRC:

The NFS server stores encrypted files on disk. NFS clients negotiate a key
when mounting/logging in, and then de/re crypt on the fly. The decrypted
data lives only in RAM on the client.

TCFS is designed to do "safe" NFS, but it can be & is used to do the sort of
thing you're talking about too, by mounting a filesystem off of yourself.
This is why I say it's a little clunky :) Aleph One recently made some
suggestions of how to make TCFS more streamlined in localhost-only setups,
but I haven't seen anybody comment on his ideas yet.

A URL I have for the TCFS project is:
We have archives of the (fairly quiet!) tcfs mailing list at:


Hank Leininger <>

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