You can't use a peer-to-peer network to hide information, which is what you'd need to actually make this little scheme work.

jedunnigan's suggestions are correct, there's also a variant of the OTP approach that doesn't even require a third party to work.

Coastermonger: Are you flexible as to what security approach can be used? The OTP toolkit is probably the best one in terms of user friendliness, and requiring little to no extra software.