Vista: Multiple Startup Keys on one USB flash drive

If I have several startup keys (.FVE files) for different Vista machines on
one USB flash drive, how does each machine know which one is correct? Is the
filename recorded somewhere in the unencypted portion of the drive? Or does
it simple try all the possible .FVE files until it finds the lucky winner?

Thanks,

Good question

There are a number of layers to the answer.
(1) The filename uses a GUID. Each key protector (refer to WMI interface) is
referenced by a GUID, these are the same GUID.
(2) The structure of the binary file contains both the GUID of the encrypted
volume and the GUID of the key protector.
(3) When decrypting the VMK, AES/CCM is used with 256-bit AES key. This is
an industry standard algorithm, that contains a nonce and a MAC (message
authentication check). If the startup key was wrong, then the MAC part of
the AES/CCM algorithm detects this and causes a failure.
(4) Should 1-3 fail, then the data would be decrypted incorrectly into
gibberish Thankfully 1-3 prevents (4).
-
Jamie Hunter [MS]

"tavis" <tavis@discussions.microsoft.com> wrote in message
news:8911F7D1-4300-4CFF-9421-CDF98F3ED857@microsoft.com...
> If I have several startup keys (.FVE files) for different Vista machines
> on
> one USB flash drive, how does each machine know which one is correct? Is
> the
> filename recorded somewhere in the unencypted portion of the drive? Or
> does
> it simple try all the possible .FVE files until it finds the lucky winner?
>
> Thanks,

Thanks again, Jamie.

I must give credit to my very inquisitive and bright colleagues for these
questions.
;-)

"Jamie Hunter [MS]" wrote:

> Good question
>
> There are a number of layers to the answer.
> (1) The filename uses a GUID. Each key protector (refer to WMI interface) is
> referenced by a GUID, these are the same GUID.
> (2) The structure of the binary file contains both the GUID of the encrypted
> volume and the GUID of the key protector.
> (3) When decrypting the VMK, AES/CCM is used with 256-bit AES key. This is
> an industry standard algorithm, that contains a nonce and a MAC (message
> authentication check). If the startup key was wrong, then the MAC part of
> the AES/CCM algorithm detects this and causes a failure.
> (4) Should 1-3 fail, then the data would be decrypted incorrectly into
> gibberish Thankfully 1-3 prevents (4).
> -
> Jamie Hunter [MS]
>
> "tavis" <tavis@discussions.microsoft.com> wrote in message
> news:8911F7D1-4300-4CFF-9421-CDF98F3ED857@microsoft.com...
> > If I have several startup keys (.FVE files) for different Vista machines
> > on
> > one USB flash drive, how does each machine know which one is correct? Is
> > the
> > filename recorded somewhere in the unencypted portion of the drive? Or
> > does
> > it simple try all the possible .FVE files until it finds the lucky winner?
> >
> > Thanks,
>