May 2004 - cypherpunks-legacy

'Taxi! Fly Me To Cleveland'
by R. A. Hettinga 18 May '04

18 May '04

Geodesic Air Travel is here. I flew out of Albuquerque last week with one of the guys from Eclipse Aviation. Okay. We were on the same plane. I was in steerage. He wasn't. :-). Cheers, RAH ------- <http://online.wsj.com/article_print/0,,SB108491821399715012,00.html> The Wall Street Journal May 19, 2004 THE MIDDLE SEAT By SCOTT MCCARTNEY 'Taxi! Fly Me To Cleveland' New Four-Passenger Jets Spur Plans for Cab-Like Air Service; Memories of People Express May 19, 2004 Perhaps as soon as next year, travelers will have a new alternative to flying commercial airlines or buying their own jet. Using a new generation of small jets that are currently in flight testing, several entrepreneurs are trying to launch "air taxi" services. The goal is to let corporate travelers bypass crowded airports and fly into smaller, local airports, at half of the current cost of chartering a jet. The most advanced air-taxi effort is coming from the man who brought the bus to air travel. Donald C. Burr -- founder of People Express Airlines back in the 1980s -- plans to launch iFly Air Taxi Inc. service next year. He has teamed up with son, Cameron, as well as his onetime nemesis, Robert L. Crandall. The former chief executive of AMR Corp. and its American Airlines, Mr. Crandall once helped run Mr. Burr's People Express out of business. Venture capitalists and aircraft manufacturers say other groups are also developing plans for air-taxi service, but none has come forward publicly yet or has had to make a Securities and Exchange Commission filing as iFly did March 29. Air taxis are also envisioned as a growing part of the nation's air-transport system in a futuristic blueprint being developed by a government task force that will report to the White House later this year. One reason for optimism that now is the right time for air taxis: The arrival of a new generation of four-passenger "micro jets" that can operate more cheaply than conventional jets. These aircraft typically are much lighter than conventional private jets, and are powered by a new generation of small, fuel-efficient engines. None of the planes are in service yet. Manufacturers are accepting advance orders, which so far are being placed by a mixture of private individuals and hopeful air-taxi operators. The new planes have the potential to revolutionize transportation. Currently, chartering private jets is extremely expensive, costing $7,000 or more for a 500-mile hop, round-trip. Fractional ownership (where you buy a "share" of an aircraft that entitles you to use it periodically) is no bargain either. Corporate-owned jets, while sometimes economical for shuttling groups of executives, are often viewed as overly expensive perks. Air-taxi service would be different, in theory at least. Mr. Burr says he can provide rides for $3 to $4 a mile, on average -- which works out to be a bit more expensive than most first-class tickets. A trip to Cleveland from Teterboro, N.J., for example, might cost $1,000 to $1,400 on average. By comparison, an unrestricted first class ticket on Continental Airlines from Newark, N.J., to Cleveland costs $1,338. iFly is expected to announce an order for Adam Aircraft jets soon. The Adam A700, which at $2 million is half of the price of the cheapest Cessna Citation jet right now, began flight tests in July 2003. The Adam jet is one of a half-dozen new aircraft like this in development. Honda Motor Co. has been conducting test flights of its HondaJet in North Carolina; Toyota Motor Corp. is also working on a jet. Eclipse Aviation Corp., run by a former software executive with considerable financial backing, says it has orders for more than 2,000 jets. Other heavy hitters are working on the most important aspect, the engines. General Electric Co. is working on the Honda jet; Pratt & Whitney, a unit of United Technologies Corp., is testing a new engine that will power the Eclipse jet; and Williams International is shrinking an engine currently used on Citation jets for the micro-jet class. It powers the Adam Aircraft jet. Corporate aviation has a solid safety record, with an accident rate per flight-hour about on par with commuter airlines, according to National Transportation Safety Board figures. Air-taxi operations also claim to offer convenience, since travelers would arrive and depart at small airports, park just a short walk from the plane, and could choose their own departure times. And taking a taxi would avoid security lines and reduce the chances of lost luggage. "It's a highly simplified charter operation," Mr. Crandall says. "We hope to run it like a limousine service." Much like airline tickets, iFly will be priced so that peak periods are more expensive than off-peak times. In addition the third and fourth seats on a "taxi" flight will be a lot cheaper than the first or second seats sold. This time, he says he intends to grow slowly. The lack of technology and aggressive growth ultimately cratered People Express, which was bought out by Continental in 1987. iFly, which has raised $6.3 million, plans to start service with two to three planes based in the New York area. It eventually hopes divide the country into as many as 13 regions, and have about 75 to 100 planes serving each region. Success may well depend on how well the company's computer systems can manage the planes, maximizing taxi fares each day while minimizing costs. The Burrs have spent three years trying to pull together a plan. Raising money was tough until big companies like GE, Pratt & Whitney, Honda and Toyota started investing in micro-jets. The National Aeronautics and Space Administration has also helped advance the air-taxi concept through a project called Small Aircraft Transportation System that has pushed research on ways to relieve airport and highway congestion, and at the same time change travel patterns and boost small communities. "We have an abundance of airspace, we just don't know how to use it well," said Bruce Holmes, associate director in the airspace programs office at NASA Langley Research Center. Dr. Holmes is also part of a congressionally mandated task force drafting a blueprint for the "Next Generation Transportation System," which has been modeling different scenarios for what transportation will be like in 2025 and beyond. The task force's report is due at the White House in December, and it will endorse air-cab or air-limo services. There are a flock of unanswered questions about air-taxi service, including the issue of whether more planes in the sky will add to congestion, or will, in fact, relieve congestion. What seems clear is that transportation in the future will take many forms, and that our choices in the future may well be better than the ones we have today. -- ----------------- R. A. Hettinga <mailto: rah(a)ibuc.com> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/> 44 Farquhar Street, Boston, MA 02131 USA "... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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al-qaeda.net node downtime
by Riad S. Wahby 18 May '04

18 May '04

I'm moving from Massachusetts to Texas, and unfortunately that means that my machine's connectivity will be in a state of flux for a while. Unless someone has a machine with a (fast, static) connection on which they want to let me host the node temporarily, al-qaeda.net will be down for some (unspecified, but hopefully not too long) time while I move. If you do have a place to put the node (I believe measl(a)mfn.org once offered such a machine, but perhaps things have changed), let me know within the next day or two and I'll move everything over before I leave. -- Riad Wahby rsw(a)jfet.org MIT VI-2 M.Eng

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Diffie-Hellman question
by Thomas Shaddack 18 May '04

18 May '04

I have a standard implementation of OpenSSL, with Diffie-Hellman prime in the SSL certificate. The DH cipher suite is enabled. Is it safe to keep one prime there forever, or should I rather periodically regenerate it? Why? If yes, what's some sane period to do so: day, week, month? If the adversary has a log of a passively intercepted DHE-RSA-AES256-SHA secured SSL communication, presuming the ephemeral key was correctly generated and disposed of after the transaction, will the eventual physical retrieval of the DH prime (and the rest of the certificate) allow him to decode the captured log? I am rather inexperienced in this area, don't want to make a mistake, and generation of 2048-bit primes is CPU-hungry enough to not decide to just throw it in without a good reason.

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Re: Reusable hashcash for spam prevention
by Fearghas McKay 18 May '04

18 May '04

and the data that Eric S. Johansson got: -=-=- forwarded text -=-=- this is frustrating. I have run through the exact same calculations and come up with a very different answer. The answers I came up with the show that at worst case, spammers with zombies would almost have enough horsepower to generate enough stamps. one of the difficult aspects of this is that I have not been able to get hard numbers on the number of zombies (it varies by an order of magnitude at least depending on the source) as I said at my MIT anti-spam conference talk, I do agree that proof of work stamps are not a panacea but they are an important component in the "drug cocktail" used to attack spam. that's why I tried very hard to build camram to be able to incorporate other anti-stamp techniques or work in conjunction with them. Another impression of a shortcoming is that they mix and match economic models. I need to go through in greater detail to find out if they have found something I missed. I do know that the cost of a PC and its operation are insignificant to the rate limiting effect of stamp generation. they also did not seem to account for different degrees of cost of doing business. Proof of work stamps will take out the low-end spammers first allowing us to concentrate efforts on higher end, better financed spammers. Fewer targets, easier to hit. They did not account for automatic inflation of postage rates when stamped Spam appears or the addition of a second tier of stamps (i.e. signatures for familiar entities/mailing lists. the problem with impact on low-end machines is important if you always generate stamps. However, for extreme low-end machines (PalmPilot and cellphones) you can always defer the computational load to a for fee service such as the ISP handling your e-mail for the device. With the rest of the low-end machines, stamped generation just takes longer, and background and once you have white listed the entity, you never need to send them a stamp again. on eco damage caused by stamp generation, again, the transition between stamps and white lists based on stamp activity illuminate that problem. It's only commercial entities who want to send you advertising unsolicited that would incur such damage. On the other hand, kill a couple of SUVs and you can generate many more stamps without worry. ;-) on zombies: I think it might be useful if the anti-spam folks spent some time developing zombie hunters and worked with various service providers to identify and shut off those machines. Additionally, ISPs should send Microsoft an invoice for every machine found and repaired. Get enough people together, you could have a substantial lawsuit. After all, the real culprit in the zombie problem is not the owner of the PC. Yes they were stupid, yes they ran something they shouldn't have, but the system should not have failed quite so easily! so am I discouraged? A little bit. I'm going to continue but it's one more naysayer I'm going to have to build arguments against. -=-=- end forwarded text -=-=- --- end forwarded text -- ----------------- R. A. Hettinga <mailto: rah(a)ibuc.com> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/> 44 Farquhar Street, Boston, MA 02131 USA "... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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Re: Reusable hashcash for spam prevention
by Fearghas McKay 18 May '04

18 May '04

and the data that Eric S. Johansson got: -=-=- forwarded text -=-=- this is frustrating. I have run through the exact same calculations and come up with a very different answer. The answers I came up with the show that at worst case, spammers with zombies would almost have enough horsepower to generate enough stamps. one of the difficult aspects of this is that I have not been able to get hard numbers on the number of zombies (it varies by an order of magnitude at least depending on the source) as I said at my MIT anti-spam conference talk, I do agree that proof of work stamps are not a panacea but they are an important component in the "drug cocktail" used to attack spam. that's why I tried very hard to build camram to be able to incorporate other anti-stamp techniques or work in conjunction with them. Another impression of a shortcoming is that they mix and match economic models. I need to go through in greater detail to find out if they have found something I missed. I do know that the cost of a PC and its operation are insignificant to the rate limiting effect of stamp generation. they also did not seem to account for different degrees of cost of doing business. Proof of work stamps will take out the low-end spammers first allowing us to concentrate efforts on higher end, better financed spammers. Fewer targets, easier to hit. They did not account for automatic inflation of postage rates when stamped Spam appears or the addition of a second tier of stamps (i.e. signatures for familiar entities/mailing lists. the problem with impact on low-end machines is important if you always generate stamps. However, for extreme low-end machines (PalmPilot and cellphones) you can always defer the computational load to a for fee service such as the ISP handling your e-mail for the device. With the rest of the low-end machines, stamped generation just takes longer, and background and once you have white listed the entity, you never need to send them a stamp again. on eco damage caused by stamp generation, again, the transition between stamps and white lists based on stamp activity illuminate that problem. It's only commercial entities who want to send you advertising unsolicited that would incur such damage. On the other hand, kill a couple of SUVs and you can generate many more stamps without worry. ;-) on zombies: I think it might be useful if the anti-spam folks spent some time developing zombie hunters and worked with various service providers to identify and shut off those machines. Additionally, ISPs should send Microsoft an invoice for every machine found and repaired. Get enough people together, you could have a substantial lawsuit. After all, the real culprit in the zombie problem is not the owner of the PC. Yes they were stupid, yes they ran something they shouldn't have, but the system should not have failed quite so easily! so am I discouraged? A little bit. I'm going to continue but it's one more naysayer I'm going to have to build arguments against. -=-=- end forwarded text -=-=- --- end forwarded text -- ----------------- R. A. Hettinga <mailto: rah(a)ibuc.com> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/> 44 Farquhar Street, Boston, MA 02131 USA "... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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Re: Reusable hashcash for spam prevention
by Fearghas McKay 18 May '04

18 May '04

This was posted on the ASRG list - the IRTF Anti Spam Research Group list, which at first reading indicates that the future for Hashcash/Camram may be limited. Eric Johansson the camram developer has some different numbers which he has just run that I will dig out and forward. f --- begin forwarded text

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Re: Reusable hashcash for spam prevention
by Fearghas McKay 18 May '04

18 May '04

This was posted on the ASRG list - the IRTF Anti Spam Research Group list, which at first reading indicates that the future for Hashcash/Camram may be limited. Eric Johansson the camram developer has some different numbers which he has just run that I will dig out and forward. f --- begin forwarded text

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Re: Reusable hashcash for spam prevention
by R. A. Hettinga 18 May '04

18 May '04

--- begin forwarded text

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Re: Reusable hashcash for spam prevention
by R. A. Hettinga 18 May '04

18 May '04

--- begin forwarded text

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Re: Diffie-Hellman question
by Anonymous 18 May '04

18 May '04

Thomas Shaddack writes: > I have a standard implementation of OpenSSL, with Diffie-Hellman prime in > the SSL certificate. The DH cipher suite is enabled. > > Is it safe to keep one prime there forever, or should I rather > periodically regenerate it? Why? If yes, what's some sane period to do so: > day, week, month? > > If the adversary has a log of a passively intercepted DHE-RSA-AES256-SHA > secured SSL communication, presuming the ephemeral key was correctly > generated and disposed of after the transaction, will the eventual > physical retrieval of the DH prime (and the rest of the certificate) allow > him to decode the captured log? The DH prime is not secret, and will not in general allow an adversary to decode the message. Only the private parts of the ephemeral DH keys used by the two sides are secret, and they are destroyed after use. The only theoretical concern is that if the DH prime were small enough, an adversary at some time in the future might be able to break the DH key exchange by calculating discrete logs mod the prime. To within a few orders of magnitude, this is thought to be equally as difficult as breaking an RSA modulus of the same size. If your prime is 2000 bits, then that should be safe for the foreseeable future, unless quantum computers turn out to be practical for breaking moduli of this size. In the unlikely event that it becomes possible to break the DH exchange by attacking the DH prime in this manner, then all key exchanges that were done using that prime would be broken (assuming they were recorded for later analysis and attack). The main work of the break is directed towards the prime itself. Once that is done, there is little additional work to break a key exchange which used that prime. This is the only reason you might want to think about changing DH primes occasionally, so that if some super technology of the future were able to attack even your 2000 bit prime, at least they'd have to run their program a few times rather than just once. But really, that's not much of a security gain, as you're only increasing the attacker's costs by a relatively small factor. And at this point the attack would have to be viewed as extremely speculative anyway. So there's not much reason to change your prime. This is unlike the case with RSA moduli, where you not only have this very hypothetical risk of a future technology breakthrough to allow factoring, but you also have to face the genuine threat that the private key will be exposed or stolen. Once that happens, all past messages encrypted with the key will be revealed. There are good reasons to change RSA moduli regularly for this reason (of course, most people don't do it anyway, because of our poor key management tools). But with DH primes, that is not a concern, as there is no long-term secret to be lost. All you have to worry about is a discrete log breakthrough, and that's not something to lose any sleep over.

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