24 KiB
- Loose Ends and Miscellaneous Topics
18.1. copyright THE CYPHERNOMICON: Cypherpunks FAQ and More, Version 0.666, 1994-09-10, Copyright Timothy C. May. All rights reserved. See the detailed disclaimer. Use short sections under "fair use" provisions, with appropriate credit, but don't put your name on my words.
18.2. SUMMARY: Loose Ends and Miscellaneous Topics 18.2.1. Main Points 18.2.2. Connections to Other Sections 18.2.3. Where to Find Additional Information 18.2.4. Miscellaneous Comments - I hate to have a section like this, but there are just some things that don't seem to fit neatly elsewhere - hopefully you found this topics with your editor search tools
18.3. Quantum Cryptography 18.3.1. "What is quantum cryptography?" + Two main flavors: + secure channels exploiting the Uncertainty Principle + Brassard, Bennett, fiber optic lines, short distances, detects tapping + Quantum cryptography - bits can be exchanged-albeit at fairly low efficiencies-over a channel - with detection of taps, via the change of polarizations + Stephen Wiesner wrote a 1970 paper, half a decade before the P-K work, which outlined this-not published until much later - speculate that the NSA knew about this and quashed the publication + factoring of numbers using a strange Many World interpretation - Shor + hearkens to my spoof about Russians - I never knew I hit so close to the mark! 18.3.2. "What about quantum cryptography?" + Exploiting Uncertainty Principle to make untappable communication lines. (More precisely, tapped lines give indication of having been tapped.) - Bennett and Brassard - faint flashes of light in a fiber optic cable used; polarized photons - Alice and Bob go through a protocol that involves them picking Linear or Circular Polarization (LP or CP); can't be simultaneously measured... - - Not likely to be important for a long time. - An additional tool, or crypto primitive building block.
18.4. Chaotic Cryptography 18.4.1. the oscillator scheme was broken at Crypto '94
18.5. Neural Nets and AI in Crypto 18.5.1. "What about neural nets and AI in crypto?" - Of limited use, at least in breaking modern ciphers. Marvin Minsky once said that if you don't understand how to solve a problem, adding randomness usually doesn't help. - The shape of the solution space is very spiky, very poorly- suited to hill-climbing or divide-and-conquer methods + Neural nets are not likely to do well with modern ciphers (e.g., RSA, IDEA, DES, etc.), mainly because of the shape of the solution space. Instead of the "rolling hills and valleys" that neural nets (and related methods, such as genetic algorithms, simulated annealing, etc.) do well in, the solution space for modern ciphers offers very little in the way of "learning" opportunities: you either have the solution (the key), or you don't.
Think of a needle standing up from a flat plain...a NN or
any other hill-climber could wander for years and never
find it. Well-designed modern ciphers like RSA and IDEA
appear to admit no analysis based on "nonrandom"
properties. If anybody has found shortcuts to factoring the
modulus in RSA, for example, they haven't let on.
I suspect there are uses in peripheral aspects, such as
guessing passwords (when people have not picked high-
entropy passwords, but have instead used familiar names).
Or in traffic analysis. Those who munch on lots of traffic
may well be using neural nets, custom signal processing,
etc. to "prepare" the captured traffic for further
analysis. A safe bet, in fact.
But the move in modern cryptology is definitely away from
using anything with "structure" that can be learned. Put
another way, neural nets and such work well in structured
environments, where there's something to _learn), but not
in the high-entropy, seemingly random world of encrypted
data.
+ AI may be useful in other areas
- protocol generation
- SIGINT
18.5.2. Evolutionary or Genetic Programming - a la Holland, Koza - RNGs
18.6. Miscellaneous Advanced Crypto Ideas 18.6.1. "Why have provably "NP-complete" problems not found uses in crypto?" - One of the great Unresolved Mysteries! Or the Holy Grail, if you will. - The issue is why have provably hard (or NP-complete, to be more accurate) problems not been used? (Factoring is not known to NP-complete...experts can correct my phrasing here if I'm misstating things.) - It would be nice if a provably hard problem, such as the domino tiling problem, or 3SAT, or other such things out of Garey and Johnson's book on NP-Completeness could be used. This would increase confidence in ciphers still further. 18.6.2. "Can cellular automata, like Conway's "Game of Life," be used for cryptography?" - Stephen Wolfram proposed use of cellular automata for crytography some years back; his collection of essays on cellular automata contains at least one such mention. Many people suspected that 1D CAs were no stronger than linear feedback shift registers (LFSRs), and I recally hearing a couple of years ago that someone proved 1D CAs (and maybe all CAs?) are equivalent to LFSRs, which have been used in crypto for many years. - Wolfram's book is "Theory and Applications of Cellular Automata," 1986, World Scientific. Several papers on using CAs for random sequence generation. P. Bardell showed in1990 that CAs produce the outputs of LFSRs.) Wolfram also has a paper, "Cryptography with cellular automata," in Proc. CRYPTO 85. - Intuitively, the idea of a CA looks attractive for "one-way functions," for the reasons mentioned. But what's the "trapdoor" that gives the key holder a shortcut to reverse the process? (Public key crypto needs a trapdoor 1-way funtion that is easy to reverse if one has the right information).
18.7. Viruses and Crypto 18.7.1. "What's the connection between Cypherpunks and viruses?" - Like, dewd, it's so kool. - Beavis 'n Butthead use PGP (actually, Eric Hughes proposed at one point that we suggest a crypto tie-in to the writers) - There's only peripheral connection. - Viruses can be spread with anonymous remailers, but digital signatures can be used to safeguard software. Signed software, no mods allowed. 18.7.2. "What about the "encryption viruses," like KOH?" - (A little far afield, but the issue does come up.) - Somebody asked about this on sci.crypt and Vesselin Bontchev said: "This topic has been debated to death in alt.security.pgp, when somebody posted KOH, without even a warning that it is a virus.....Both viruses indeed use the IDEA cipher - the same that is used both by SecureDevice and SecureDrive. However, the viruses pose some significant threats to the integrity of your data, exactly because of their viral replication means.....Also, if you aquire it by viral means, you do not get the doumentation and one utility, both of which are essential for the proper usage of the product - thus proving one more time that its viral capabilities are unnecessary and harmful. Also, the virus does not come in source, which means that it could have some hidden backdoors or simply security flaws, and you have no way to check this or to fix them. At last, in some cases the virus could destroy valuable information during its replication process." - "In short - don't use them. You will gain nothing over using stand-alone encryption programs, and you'll expose your data's integrity to significant risks. Those viruses are completely useless and even harmful; they have been created with the only reason to condone the illicit activities of the virus writers, by claiming that computer viruses can be "useful"." [Vesselin Bontchev, sci.crypt, 1994-08-31] 18.7.3. "What about viruses? Are there any ties to crypto and Cypherpunks themes?" - No direct link that any of us see clearly. Occasionally a virus fan sees the "punks" name and thinks we're involved in writing viruses. (Actually, a few folks on the list have virus expertise.) - Crypto may protect against viruses, by having code signed. And the reliance on self-responsibility and self-protection is in contrast to the legal approach, which tends not to work too well for virus protection (by the covert nature of many viruses). 18.7.4. "What interests do Cypherpunks have in viruses?" - Not much, though the topic comes up periodically. - Some overlap in the communities involved. - And there are some virus methods which use forms of encryption. - Also, digital signatures on code can be used to ensure that code has not been modified since being released by the original author.
18.8. Making Money in Crypto 18.8.1. "How can I make money in crypto?" - crypto experts are hired by software companies + start up companies - a tough road - not clear that even Phil Zimmermann has made money - and even RSADSI is facing a challenge (hasn't gone public, not a cash cow, etc.) - There may be an explosive growth--the phase change I often talk about--and many opportunities will emerge. But, having said this, I still don't see obvious opportunities right now. And starting a company based on hope and ideology, rather than supplying a real market or pushing real technology (market pull vs. technology push argument) seem misguided.
18.9. The Net 18.9.1. Limitations of the current net - interoperability + subsidized, not pay as you go - makes spamming inevitable, doesn't allocate resources to those who want them the most - this will require digicash in a better form than most users now have access to - sysadmins get worried - encryption sometimes banned - common carrier status not clear - general cruftiness of Net ("imminent death of Usenet predicted")
18.10. Duress Switches, Dead Man Switches 18.10.1. "What about "duress" codes for additional security?" - Where a harmless decrytion can be done, or an alarm sent. + Examples - sending alarm, like an under the counter alarm button - decrypting a bank card number for a lesser-value account - two sets of books (not strictly a "duress" code, unless you view the IRS as causing duress) - alarms to associates, as in cells - " Having a separate authentication mechanism that is used under duress is a very good idea that some existing systems already employ.... From a systems point of view, it is hard to figure out exactly how the system should respond when it recognizes a duress authentication....The safe inside the ATM machines used by BayBanks (Boston Mass) can be opened with two combinations. One combination sends an alarm to the bank via a separate phone line (not the one used to perform the ATM transaction). The alarm phone line is also connected to a conventional panic switch." [Bob Baldwin, Duress Passwords/PINs/Combinations, 1993-11-18] 18.10.2. Duress switches, dead man switches, etc. + "Digital flash paper," can be triggered to erase files, etc. - (BATF and DEA raiders may have sophisticated means of disabling computers) + Duress codes..."erase my files," ways of not giving esrowed information unless proper code is given, etc. + "Don't release if I am under indictment" - interesting issues about secret indictments, about publicity of such cases, access to court records by offshore computers, etc. 18.10.3. Personal security for disks, dead man switches + I have heard that some BBS operators install dead man switches near the doors to rooms containing their systems...entering the room without flipping the switch causes some action to be taken - erasing a disk, dumping a RAM disk (a dangerous way to store data, given power failures, soft errors, restarts, etc.)
18.11. Can Encryption be Detected? 18.11.1. "Can messages be scanned and checked for encryption?" - If the encryption produces markers or other indications, then of course. "BEGIN PGP" is a pretty clear beacon. (Such markers assists in decryption by the recipient, but are not essential. "Stealth" versions of PGP and other encryption programs--such as S-Tools for DOS--don't have such markers.) - If the encryption produces "random-looking" stuff, then entropy measures and other statistical tests may or may not be able detect such messages reliably. Depends on what non- encrypted messages look like, and how the algorithm works. + Steganography: - making messages look like normal ones - tucking th ebits in with other random-like bits, such as in the low-order bits of images or sound files - The practical concern depends on one's local political environment. In many countries, mere suspicion of using crypto could put one in real danger.
18.12. Personal Digital Assistants, Newtons, etc. 18.12.1. "Are there cryptographic uses for things like Newtons?" - Probably. Eventually. Digital wallets, portable key holders, local agents for access, etc. + Meanwhile, a few encryption programs exist. Here's one: - -> nCrypt, the strong cryptography application for Newton: -> ftp.sumex-aim.stanford.edu/info-mac/nwt/utils/n-crypt- lite.hqx
18.13. Physical Security 18.13.1. "Can fiber optical cables be tapped?" + Yes. Light can escape from the fiber in bends, and "near- field" tapping is theoretically possible, at least under lab conditions. Active measures for puncturing cable shields and tapping fibers are also possible. - "The Fed's want a cost effective F/O tap. My company was approached to develop such a system, can be done but not cheap like copper wire tapping." [ domonkos@access.digex.net (andy domonkos), comp.org.eff.talk, 1994-06-29] - Los Alamos technology? 1990?
18.14. Attacking Governments 18.14.1. "termites" (rumors, psy-ops) that can undermine governments, followed by "torpedoes" (direct attack) 18.14.2. WASTE (War Against Strong, Tamper-resistant Encryption).
18.15. Cypherpunks List Issues 18.15.1. too much noise on the list? - "Of all the lists I'm subscribed to, this is the only one that I read every article in. Even the "noise" articles. Humans being what they are, the noise is needed to help decide the direction of the group. Besides, for those of us who are just starting on our journey through crypto-underworld need the noise to help familiarize ourselves with how crypto works. I've learned more from the informal ramblings than I've gathered out of all the formal and/or mathematical postings to date." [Patrick E. Hykkonen, 5-25-93]
18.16. Tamper-Resistant Modules 18.16.1. TRMs--claims that "Picbuster" processor can be locally overwritten with focussed or directed UV (OTP) 18.16.2. tamper-resistant modules have some downsides as well - cash registers for ensuring compliance with all relevant sales tax, value-added tax (VAT), and rationing rules; a tamper-resistant module cash register could be the enforcement mechanism for a national security state. - "observers"
18.17. Deeper Connections 18.17.1. In several places I've referred to "deep connections" between things like crypto, money, game theory, evolutionary ecologies, human motivations, and the nature of law. By this I mean that there are deeper, unifying principles. Principles involving locality, identity, and disclosure of knowledge. A good example: the deep fairness of "cut-and-choose" protocols- -I've seen mention of this in game theory tesxts, but not much discussion of other, similar protocols. 18.17.2. For example, below the level of number theory and algorithms in cryptology lies a level dealing with "identity," "proof," "collusion," and other such core concepts, concepts that can almost be dealt with independent of the acual algorithms (though the concrete realization of public key methods took this out of the abstract realm of philosophy and made it important to analyze). And these abstract concepts are linked to other fields, such as economics, human psychology, law, and evolutionary game theory (the study of evolved strategies in multi-agent systems, e.g., human beings interacting and trading with each other). 18.17.3. I believe there are important questions about why things work the way they do at this level. To be concrete, why do threats of physical coercion create market distortions and what effects does this have? Or, what is the nature of emergent behavior in reputation-based systems? (The combinatiion of crypto and economics is a fertile area, barely touched upon by the academic cryptology community.) Why is locality is important, and what does this mean for digital cash? Why does regulation often produce more crime? 18.17.4. Crypto and the related ideas of reputation, identity, and webs of trust has introduced a new angle into economic matters. I suspect there are a couple of Nobel Prizes in Economics for those who integrate these important concepts.
18.18. Loose End Loose Ends 18.18.1. What the core issues are...a tough thing to analyze - untraceablility as a basic construct has major implications + can often ask what the implications would be if, say: - invisibility existed - untraceability existed - By "tough to analyze" I mean that things are often coflated, mixed together. Is it the "reputations" that matter, or the "anonymity"? The "untraceability" or the "digital money"? 18.18.2. Price signalling in posts...for further information + When an article is posted, and there is more complete information available elsewhere by ftp, gopher, mosaic, etc., then how is this to to be signalled without actually advertising prominently? - why not a code, like the "Geek code" so many people put in their sigs? The code could be parsed by a reader and used to automatically fetch the information, pay for it, etc. (Agents that can be built in to newsreaders.) 18.18.3. "What should Cypherpunks support for "cable" or "set-top box" standards? - Caveats: My opinions, offered only to help frame the debate. And many of us reject the idea of government- mandated "standards," so my phrasing here is not meant to imply support of such standards. + Major alternatives: + Set-top box, with t.v. as core of access to "information superhighway." + Problems: - limited number of channels, even if "500 channels" - makes t.v. the focus, loses some other capabilities - few consumers will have television sets with the resolution capabilities that even current computer monitors have (there are reasons for this: size of monitors (related to viewing distance), NTSC constraints, age of televisions, etc.) + Switched-packet cable, as in ATM or even SONET (Synchronous Optical Network) access + Advantages: - Television is just one more switched-packet transmission, not using up the bandwidth + Radical Proposal: Complete deregulation + let cable suppliers--especially of optical fibers, which are small and unobtrusive--lay fibers to any home they can negotiate access to - e.g., by piggybacking on telephone lines, electrical cables, etc. (to remove the objection about unsightly new poles or cables being strung...should not be an issue with fiber optics) - let the market decide...let customers decide + In my view, government standards are a terrible idea here. Sure, NTSC was an effective standard, but it likely would have emerged without government involvement. Ditto for Ethernet and a zillion other standards. No need for government involvement. - Of course, when industry groups meet to discuss standards, one hopes that antitrust laws will not be invoked. 18.18.4. minor point: the importance of "But does it scale?" is often exaggerated - in many cases, it's much more important to simply get something deployed than it is to worry in advance about how it will break if too many people use it (e.g., MacDonald's worrying in 1955 about scalabilty of their business). - Remailer networks, for example, may not scale especially well in their current form...but who cares? Getting them used will allow further refinement.