As I said in my "Nightmare on Crypto Street" piece, it seems that Peter counters every one of our counterarguments with some variant of "won't matter--they'll have a dozen agents and 20 MIT graduates looking for evidence." Or, "won't matter, the Bill of Rights will be suspended for the duration of the Emergency." Well, it's hard to argue with such points. On a few plausibility points, or on technical points (as with the meaning of "noise," for example), there's still a basis for a debate. At 9:02 AM -0800 11/8/96, Peter Hendrickson wrote:
Where will you keep your secret key? Remember, when they go through your house they bring 20 young graduates from MIT who are just dying to show how clever they are and save the world at the same time.
Unlikely they'll be able to find or marshall 20 MIT grads. Didn't happen when they raided Steve Jackson Games as part of Operation Sun Devil and hauled away all of his equipment. It probably _did_ happen with the raid on the Unabomber's cabin, except probably the numbers of MIT grads were fewer and their specialties were in other areas. Where do you keep your secret key? On your disk. However, one's PGP _passphrase_ is what is really important (though both are important). Without the passphrase, the secret key is worthless. Now of course some people write down their passphrases on Post-It notes, etc., and certainly keystroke capture programs may be running (inadvertently, deliberately, or even via previous blackbag job plants, as many of us have noted over the years). However, a properly memorized passphrase, of sufficient length and entropy to make exhaustive search impractical, and proper "crypto hygiene" will go a long way toward making such raids ineffective. And there are several reports of such raids turning up PGP-encrypted files which the cops and investigators have been unable to crack. PRZ speaks of being asked to help, and some others here on this list have mentioned similar situations. The Church of Scientology has been seeking "PGP experts" to help them read some files they believe may help them get someone punished. Basically, without the passphrase, not much can be done. (I expect the "crypto hygiene" issue to get better, not worse. It is likely that "crypto dongles" and PDAs will soon drop in price enough such that one can store one's private key on a dongle, smartcard, or PDA and enter the passphrase with a keypad built in...this dramatically cuts the risk that a keystroke capture program is being run, or that a TEMPEST van is trying to capture the keystrokes (LCD and low-power CMOS circuitry don't generate a helluva lot of Van Eck radiation :-} .) And there are the familiar low-tech versions of protecting some keying material, such as "rat lines" into neighboring apartments. A few years ago we talked about how hacker-friendly buildings could easily be wired up with fibers and LANs such that files and key material were scattered in multiple sites, with various "dead man switches" to shut off access should a raid occur. Search warrants would of course be problematic (and the Bill of Rights frowns on blanket searches for, say, 40 apartments on the suspicion that a needed file may be on the hard disk of a machine in one of the 40 apartments). Finally, on this point, "perfect forward secrecy" is possible with several crypto protocols (notably, Diffie-Hellman). There is no stored keying material left behind. Adapting this approach for other uses is likely to be more popular in the future. (I certainly agree that text versions of "How to Make Sarin" are always going to be incriminating in a legal case, but crypto is not the main issue.)
This is the essence of steganography and the nature of signal and noise are fundemental principles of information theory.
The concept of noise is not all that well defined, however. There is no way to look at a signal and say "this is all noise." Sometimes physical theories may lead you to believe that it is all noise. That is fine for many applications, but when becomes less convinced of things if the consequences are severe.
Actually, you've got it turned around. What is really hard to do, and what is needed by a prosecutor seeking to prove a case, is to prove "this is *not* noise." As we've talked about for several years, storing and sending lots of noise is a Good Thing. "Yes, FBI Agent Mulder, that is a noise packet I sent." The claim that people will be thrown in prison for storing apparently-random noise on their disks, or even sending it in their writings, is ludicrous. Not so long as the Bill of Rights stands. Given the "Nightmare on Crypto Street" scenario of mass pogroms and suspension of the Constitution, maybe not. But I find this scenario implausible and not really worth worrying about overmuch. --Tim May "The government announcement is disastrous," said Jim Bidzos,.."We warned IBM that the National Security Agency would try to twist their technology." [NYT, 1996-10-02] We got computers, we're tapping phone lines, I know that that ain't allowed. ---------:---------:---------:---------:---------:---------:---------:---- Timothy C. May | Crypto Anarchy: encryption, digital money, tcmay@got.net 408-728-0152 | anonymous networks, digital pseudonyms, zero W.A.S.T.E.: Corralitos, CA | knowledge, reputations, information markets, Higher Power: 2^1,257,787-1 | black markets, collapse of governments. "National borders aren't even speed bumps on the information superhighway."