Naive question about encrypted disks

[Robert Krten]

I've read a few articles and papers on both encryption and the encrypted
filesystems available under FreeBSD, and have what probably amounts to
a naive question :-)

I've read that if you know the plaintext, or parts of it, then obtaining
the key is possible (maybe not "trivial", but "possible").

Assuming the above is true, then the question I have is, when you encrypt
the entire disk, aren't there bits of plaintext that you can derive?  I'm
thinking of meta data like what newfs leaves behind -- wouldn't it be possible
to assume/guess the location and content of at least some of that meta data,
and thus be able to then obtain the key?  Or are the pieces of meta data
that you can reliably guess at too small to be of use?  Or... ?

Like I said, I'm not an expert on crypto or filesystems by any stretch :-)

Thanks in advance,
-RK

--
Robert Krten, PARSE Software Devices
Realtime Systems Architecture, Consulting, Books and Training at www.parse.com
Looking for Digital Equipment Corp. PDP-1 through PDP-15 minicomputers!