Let me briefly elaborate on a point I made in my last post:
For voice use, this may be so (but I think pre-encryption before Clipper is still possible....see discussion at the end). But for the forthcoming _data encryption_ use (Skipjack, etc.), I don't see how "pre-encryption" can be detected, much less blocked, banned, or otherwise interfered with. After all, "data are data."
In both this data case and the Clipper voice case, I am assuming the keys for the pre-encryption are negotiated by either prearrangement or by some back-channel, and don't involve D-H or any other such protocol through the Skipjack or Clipper system. (Perhaps this situation, where a bunch of key exchange protocols must be gone through before communication takes place, is what Hal Finney was referring to when he said that the Clipper proposal looks like it will make multiple encryption impossible.) Most of my (few) encrypted communications are by this kind of prearrangement, with PGP being the most obvious case of this, and so a multiple encryption scheme is workable. With voice encryption, I guess the Clipper system will not be very cooperative with D-H and similar protocols. But it will still be possible: 1. Use the Clipperphone to establish who one is communicating with. Alice and Bob thus start talking to each other. 2. Alice says: "Switch to PGP-Voice with my P-K" (and so on). 3. Bob and Alice are thus communicating with PG-Voice, with Clipper doing a further encryption. If the Feds get a warrant to get the Clipper keys, then all they get is PGP-Voice-encrypted junk. Clipper then serves the admirable purpose of _covering_ the further use of encryption! --Tim May -- .......................................................................... Timothy C. May | Crypto Anarchy: encryption, digital money, tcmay@netcom.com | anonymous networks, digital pseudonyms, zero 408-688-5409 | knowledge, reputations, information markets, W.A.S.T.E.: Aptos, CA | black markets, collapse of governments. Higher Power:2**859433 | Public Key: PGP and MailSafe available.