How to create"official" off-line repository

[Hai Zaar <haizaar@haizaar.com>]

Good day dear list!

I work for organisation that has its development network off-line and
I want to setup a Debian with current Lenny release.
Creating on-line mirror and bringing it in on USB disk is not an
option due to security measures.

What do you suggest?
I can download binary DVDs, merge them into single file tree, rebuild
Packages/Release files with reprepro or similar, but... the repository
will not be signed and I guess net-install CD will complain. Even if I
sign it myself, I will need to remaster installer CD to include the
correct key.

So, Is there any way to reconstruct officially signed repository from
DVDs, or am I just on a really wrong way on achieving my goal?

-- 
Zaar