Encrypted baselines

One annonying thing about being a consulting company now is every once
and a while we get a client who specifically requests only one of the
partner's works on their code so as to keep it as secret as
possible... we have just that case now where we want to keep the
baseline on the same machine as the rest of our baselines but need to
encrypt it (this is a legal requirement of the client and not our idea
;-))... any advice on how to do this?