December 2003 - cypherpunks-legacy

Re: Digital Cash
by jsday＠THUNDER.LakeheadU.CA 17 Dec '03

17 Dec '03

Mike Duvos <mpd(a)netcom.com> wrote: > Assuming the transactions are done via a tamperproof module > distributed by the issuer, and the math is arranged such that > using a note in multiple transactions reveals the perpetrator, > the system prevents anonymous double-spending while still > providing all the benefits of digital cash. How does the 'tamperproof' nature of the software help at all? It's still possible to double-spend in any off-line cash system by making multiple copies of the tamper-proof modules.. the only security provided is in obscuring the algorithm. Speaking of digital cash, many thanks to the author of the 'magic money' software. I am in the process of integrating it with a local bulletin board, which should hopefully be available on the net sometime this summer. :::*::: Jeremy S. Day.

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Electronic cash System
by walter kehowski 17 Dec '03

17 Dec '03

I remind the list of Matthew J. Ghio's March 18th FWD of an announcement of a highly efficient electronic cash system created by Stefan Brands <brands(a)cwi.nl>. The documentation can be obtained from ftp.cwi.nl in pub/brands. I've downloaded it and printed it all out - it's about 100 pages - and very interesting. Walter A. Kehowski <wak(a)next1.math.pitt.edu>

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Re: Digital Cash
by Hal 17 Dec '03

17 Dec '03

I sent mail to Stefan Brands yesterday asking about what kind of information is retained by the (hardware-based) observer in his digital cash system. Brands has worked with Chaum in the past and is now seeking funding (via Usenet, apparently) for development of his own digital cash and anonymous transaction technology, which he claims is greatly improved over existing systems in terms of memory and computation requirements. Brands explained that the way his system works, the user *never* has all the information needed to represent the "digital coin". Instead, the user has part of the information, and the tamper-resistant observer chip has the other part. To spend the coin, the user and the chip have to cooperate in the protocol. Then the chip can mark its own information about that coin as having been spent, or even erase it altogether. It is this change in the internal state of the observer chip which lets it prevent double-spending (and which arguably could be defeated in any software rep- resentation of an observer). I have always been skeptical of this observer-chip approach, because it wasn't clear that it was feasible to make a tamper-resistant chip economically, and because the specialized hardware that would be required would prevent the system from being used on widely-available PCs. However, now we see that our military rulers apparently trust tamper-resistant technology well enough to put it into thousands of public hands, without fear that even one chip will be opened and read. Breaking an observer only lets you double-spend the coins it holds, while breaking Clipper allows you to permanently defeat the escrow provisions of the whole system. So this suggests that the technology is adequate for observers. As for the specialized hardware, probably a more realistic picture of the digital cash user of the future is someone holding a PDA in his hand, with possibly an infrared or cellular modem link, rather than the hacker sitting at home in front of his PC. In that context it may be realistic to imagine custom PDA's which support secure offline cash as a practical product. Hal

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Clipper (again)
by dwomack＠runner.utsa.edu 17 Dec '03

17 Dec '03

This is probably erroneous logic but... 1. Mr Davis of The New Republic sends parts of his article via modem. The article (unencrypted) is intercepted by persons unknown. Mr. Davis receives a cryptic (pun intended) call in his room about the transmissions. 2. The Clinton Administration wants Clipper to facilitate monitoring of communications. 3. The Government would escrow clipper keys. 4. What keeps someone in a high government office from misusing these keys? Especially since item 1 is illegal due to antiwiretap laws anyway? I e-mailed a copy of this to Rush...since a lot more people are excited about Whitewater than about Clipper, it seems like it might make a decent tie-in... Comments? Regards, Dave

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Dutch PGP ban
by Bradley W. Dolan 17 Dec '03

17 Dec '03

There are things about the impending PGP ban in the Netherlands which I can't understand. I lived in Wolfheze, The Netherlands, much of last year. The Dutch like to think of themselves as an open, tolerant society. In many ways, they are. Where they are not, they are usually subtle. This time, they are hardly being subtle. I don't know what that means. bdolan(a)well.sf.ca.us

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Re: Clipper (again)
by GRABOW_GEOFFREY＠tandem.com 17 Dec '03

17 Dec '03

dwomack(a)runner.jpl.utsa.edu writes: >4. What keeps someone in a high government office > from misusing these keys? Especially since > item 1 is illegal due to antiwiretap laws > anyway? Nothing!!! That's the whole point! I don't remember who said it first, although I think it was someone on this list, but key escrow is just like giving the gov't a copy of your house keys, just in case they get a court order to search your home. (This assumes you have a break-in proof house I don't know about the rest of you, but a gov't with my house key makes scares the $*&!!@ out of me! G.C.G. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | Geoffrey C. Grabow | "What we demand are rigidly defined | | Oyster Bay, New York | areas of doubt and uncertainty!" | | | -------------------- | | grabow_geoffrey(a)tandem.com | Clipper, SkipJack & Digital Telephony | | | JUST SAY NO!!! | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.3a mQCNAiz/qhsAAAEEAN4QxTfSBoeP/FCiaX0/KmCkl6BcKRa1PeoP6ZlPWydg1nOx yZAk8pIdgiGxxgiMBMsqD+SrU+Sl1Fx1AdJ14HJsBp1V6G4rBTZqvFpbNPCfrQfz K/Apg+7bBpi5Qv+sQ0TWIy38zp/laArgcdUOpE4oE2UOUBVEtYvm47K2P+i5AAUR tC9HZW9mZnJleSBDLiBHcmFib3cgPGdyYWJvd19nZW9mZnJleUB0YW5kZW0uY29t Pg== =2NWi -----END PGP PUBLIC KEY BLOCK-----

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WinPGP 1.0 is available!
by GRABOW_GEOFFREY＠tandem.com 17 Dec '03

17 Dec '03

My partner and I have just completed work on a Windows interface to D PGP 2.3a called WinPGP. This program gives you the easiest way to use PG from your Windows environment. It is available (or will be VERY soon) via anonymous FTP on ftp.eff.o Mech(a)eff.org will make an announcement with the details of its location. Cypherpunks write code! Enjoy, G.C.G. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | Geoffrey C. Grabow | "What we demand are rigidly defined | | Oyster Bay, New York | areas of doubt and uncertainty!" | | | -------------------- | | grabow_geoffrey(a)tandem.com | Clipper, SkipJack & Digital Telephony | | | JUST SAY NO!!! | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----BEGIN PGP PUBLIC KEY BLOCK----- Version: 2.3a mQCNAiz/qhsAAAEEAN4QxTfSBoeP/FCiaX0/KmCkl6BcKRa1PeoP6ZlPWydg1nOx yZAk8pIdgiGxxgiMBMsqD+SrU+Sl1Fx1AdJ14HJsBp1V6G4rBTZqvFpbNPCfrQfz K/Apg+7bBpi5Qv+sQ0TWIy38zp/laArgcdUOpE4oE2UOUBVEtYvm47K2P+i5AAUR tC9HZW9mZnJleSBDLiBHcmFib3cgPGdyYWJvd19nZW9mZnJleUB0YW5kZW0uY29t Pg== =2NWi -----END PGP PUBLIC KEY BLOCK-----

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Smile For Big Brother
by John K Clark 17 Dec '03

17 Dec '03

-----BEGIN PGP SIGNED MESSAGE----- I'm an engineer at a TV station, one of our microwave receivers at the 800 foot level of our broadcast tower has been getting an odd signal for almost 3 weeks, it's black and white video of a house and it's on 24 hours a day 7 days a week. Out of curiosity I decided to find the house, it wasn't too hard I knew the bearing and I knew exactly what the house looked like. It turns out the house is in a middle class neighborhood in Miramar Florida (about 30 miles north of Miami). The tiny camera and antenna are crudely mounted with duct tape on a telephone pole across the street , it looks like it taps into the power lines for electricity. Nobody would ever notice it unless you knew precisely where to look and what to look for. We are receiving the signal at 2458 megacycles but I think that's a second harmonic, the primary signal must be at 1229 meg, a government frequency, known to be used by the DEA. John K Clark johnkc(a)well.sf.ca.us -----BEGIN PGP SIGNATURE----- Version: 2.3a iQCVAgUBLZJ3qnwRpTAWSvwVAQFsgwP8D+JmENH434G8QArys35R75dab5PA2ZHY PGLhH9u/hQh2kof3ZKjPtL1wfXlBvPRMwqBCJJWmkb9dDOvhxp4izc7eLMm/m8NK cYrii6gqz+E6c7V+A5ONhlqRxnw7mP0pOJ8wGI06lDneYb55SvnBIbssshYhFcTV kOb0tKG0MxY= =bvp/ -----END PGP SIGNATURE-----

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Re: Digital Cash
by Hal 17 Dec '03

17 Dec '03

I too would like to hear more about tamper-proof software modules. They would be a natural for software implementations of Clipper (although perhaps too slow for many applications). Imagine running the Clipper algorithm on your own computer and it comes out with your key exposed to listeners armed with the proper black box, yet you cannot disable this exposure. Interesting thought. I doubt that these would work as digital cash observers, though, even if possible. It seems to me that the digicash observer has to retain some internal state. In effect, it has to remember which coins you have spent and which you have not. You can cheat, then, by checkpointing your computer just before spending a coin. After you spend, you restore the computer to exactly the same state it was in before you spent it. You then go somewhere else and spend the coin again. The observer has no way of knowing that these games have been played with its state, yet you have obtained twice the value of the coin. Most of the observer-based protocols are also after-the-fact double- spending-detection protocols as well, so that if the observer is defeated you can still catch the miscreant eventually. But the two problems with this are, first, that it prevents the client from being anonymous to the bank, and second, that the cheater can still multiple-spend quickly and then escape the country before being caught. It was pointed out on sci.crypt some months ago the irony that Chaum's privacy-preserving cash relies on similar tamper-resistant technology to the privacy-destroying Clipper chip. Hal

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Insecurity of DES?
by Matthew J Ghio 17 Dec '03

17 Dec '03

There's been a lot of talk about how "easy" it is to break DES. As a mental exercise I decided to see just how difficult it would be for me if I really wanted to break a DES key. There are 116 publicly availiable unix workstations here on campus (DEC 3100s). Between 12 am and 8 am, there are rarely more than 50 users on the systems, including remote users. I could probably run processes on 50 of the unused machines for a few hours every night without being too much of a nuisance. Assuming I could try a million DES decryption operations a second on each (gross overestimation), how long would it take to brute force a DES key? Let's suppose for sake of argument that I could get the machines all day: 2^56 keys / 50 cpus / 1,000,000 per second / 60 seconds / 60 minutes / 24 hours = 16680 days = 45.7 years Of course, specially-designed hardware would be much faster.

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