From: "Perry E. Metzger" <perry@imsi.com>
If you suspect that some of the non DOD/NSA cyphers might be broken, but you are not ready to employ one-time-pads, then you should threshold you mesages into N parts so that all N are needed to recover the original. Then encrypt each part under a different cypher.
Its far simpler to encrypt your message with multiple systems, one after another, than to break it up in the manner you suggest, and the security is in fact better that way than in the manner you suggest.
Why? If you XOR-split the message and encrypt each mask differently, you are /guaranteed/ that all of the encryption methods must be broken to retrieve the original. If you use repeated encryption, this is much harder to prove, and not always true. There's a result that if you choose the first cipher unwisely, you're hosed no matter what you do on top of it. Eli ebrandt@hmc.edu