ecryptfs-users team mailing list archive

[Fredrik Thulin <fredrik@xxxxxxxxxx>]

On Sun, Apr 10, 2011 at 4:17 PM, Serge Hallyn
<serge.hallyn@xxxxxxxxxxxxx> wrote:
....
> Cool.  Now the other thing I don't like is having the username:pwd
> pushed to the yubikey, only bc it's usb and i dunno, I can just see
> someone coming up with a sneaky way to grab that.

I don't like it either - I mean there is even USB over IP (even though
that approaches the old "if it hurts, don't do it").

I think that brings us to exploring either version 1 or 2 of the
"rolling challenges" I described in my previous e-mail.

My initial questions are then

- is it a good or bad idea to re-wrap your mount passphrase on each mount?

- where should the required metadata be stored? In scheme 1 this would
be the next expected response, in scheme 2 the AES key of the Yubikey
encrypted with the next response, and the next challenge in clear text

- how to make this either completely separate from eCryptfs, or vendor
neutral enough for you to think it is a good idea to include it in
eCryptfs

> Does it help at
> all to have send sha1sum(username:pwd) to the yubikey instead?  It also
> helps with your concerns about sufficent salt, right?

I think the current BCP is to use Password-Based Key Derivation
Function 2 (PBKDF2) with a sufficiently large number of iterations.
Wikipedia says the iPhone4 uses 10,000. You come very close with your
suggestion =).

/Fredrik