Absolutely - that's one of the reasons this is so exciting. As the other responder pointed out, this particle is weakly interacting and so we couldn't directly detect it, but it would show up as "missing energy". For instance, you could get a reaction at LHC on the lines of
proton + antiproton -> very energetic gluons -> squark + antisquark -> neutralinos + lots of other junk.
You could detect all of the other junk and measure its energy and momentum, and you'd see that there's a giant difference between that and the initial beam energy, so the difference must be particles that escaped your detection. Similarly you could measure the "missing charge" and so on, so you get a pretty good fix on what escaped.
The only catch is that 134GeV is actually about the absolute max that LHC will be able to see. The problem is that, while the interaction energy is about 2TeV (once everything's at full spin), the particles are protons and antiprotons. At these energies, you have to think of each of these as composite objects; bound states of three quarks (antiquarks) and a lot of gluons. The actual scattering is a quark off an antiquark, so each constituent particle has only about 1/7 of the total beam energy. On top of that, because of various conservation laws neutralinos (or any other SUSY particle) have to be created in pairs, so you need a lot of energy to do this.
But finding these particles (the buzzword is 'LSP,' Lightest Supersymmetric Particle) is one of the primary missions of LHC.
Several people seem interested in what dark matter is and whether its existence is a certain thing or a theory. So here's some stuff from the science end --
The matter you can actually see through a telescope is really only luminous matter; things which are directly emitting (a great deal of) light. Namely, stars, quasars, occasionally black holes (which are black but infalling matter creates huge X-ray jets) and things like that. Anything else, by definition, is "dark matter." (So by definition, you and I are made of dark matter - this is not generally that wierd a stuff)
The reason we know dark matter is there in large quantities is by measuring the motion of stars in galaxies and so on. Basically, we understand how gravity works pretty well (at least on astrophysical scales) and so by watching the motions and orbits of luminous objects, we can work backwards and find the distribution of mass in the universe. From this we find that only about 10% of all mass is luminous - the rest is "dark matter."
Now, it turns out we can find out substantially more about dark matter from these gravity measurements. (There are a lot of different kinds of measurements which I won't go into; suffice it to say that they all more or less agree) For one thing, we can tell how it clumps up, and from that deduce some things about its internal structure. For example, dark matter made out of heavy noninteracting particles (say about the mass of an iron nucleus) will move around very differently from dark matter made out of very light fast particles, which will move differently from large lumps of matter each about the size of a star, and so on.
The basic types of dark matter are:
Hot Dark Matter: (HDM) Small light particles moving about at close to the speed of light. Measurements suggest that there isn't much of this around, not enough to make a huge difference. Neutrinos would fall into this category.
Baryonic Cold Dark Matter: (Baryonic CDM) Heavy particles in the form of ordinary nuclei and atoms. Up to and including ourselves. This category also includes "MACHOs" (An acronym whose expansion I can't remember right now), which are essentially star-sized or bigger objects which we can't see. Brown dwarfs, large gas giants, and so on. Large dust clouds also fall into this category.
Non-Baryonic CDM: CDM means that the particles in question are heavy and so move much slower than the speed of light. Non-baryonic means that they're not made up of ordinary nuclei. This category includes what are called WIMPs (Weakly Interacting Massive Particles), which are any sort of big, heavy particle that doesn't interact much with other matter in the universe. (e.g., it can't have an electric charge, since that would make its dynamics very very unlike experimental data)
The reason WIMP searches are so cool is that any particle that turns out to be a WIMP will probably be very interesting in its own right. I can't explain all of the details in something of this length, but there is a symmetry called Supersymmetry (SUSY) which is postulated to exist. There are lots of good theoretical reasons to believe in it (for the technically minded: Grand unification doesn't work entirely right without SUSY, and you can't introduce fermions into string theories without SUSY.) and by now everyone is pretty much expecting to discover it experimentally soon; in fact, a discovery that SUSY doesn't exist would be even more interesting than a discovery that it does.
The reason I bring up this whole dreary story is that SUSY predicts that for every particle of ordinary matter (electrons, protons, photons, etc.) there is another related particle, its superpartner. A direct detection of a superpartner would be both a vivid confirmation of SUSY and incredibly useful experimental data about the structure and nature of the universe. (There are armies of physicists who are ready to strip every imaginable drop of information out of data right now. People have been waiting for this for a while.)
And lo and behold - the superpartner of the photon, called the neutralino, happens to have some properties that would make it a great candidate for a WIMP. It interacts very weakly indeed; for comparison, the Coulomb force between two electrons is proportional to 1/r^2, where r is their separation. The force between two neutralinos would scale something like e^(-r/r0)/r^2, where r0 is a characteristic distance on the order of perhaps 10^-20 meters. They're also stable - due to some conservation laws (analogous to conservation of electric charge, which makes circuits work) they can't decay into anything else, so once they're created, you're pretty much stuck with them drifting through the universe. And they're heavy - experimentally, their mass should be somewhere between 80-a few hundred GeV. (For comparison, a Hydrogen atom has a mass of just over 1GeV)
Now the Rome group is claiming to have detected WIMPs of masses somewhere between 52 and 134 GeV, which are candidates to be neutralinos. This will definitely spark some excitement and a lot of discussion. What happens next is that people are going to be reading this and arguing over every detail of their data analysis and so on, and other people will try to replicate their results. If this is confirmed, it represents a big step in understanding both the large-scale nature of the universe (WIMPs, and the nature and origin of dark matter) and its very small-scale structure. (SUSY, the fundamental interactions of matter)
OTOH, one shouldn't get too excited yet -- this represents an interesting result but it still has to go through a very rigorous checking and repeating process. It has happened (quite a few) times before that interesting signals have been observed which later turn out to be something very ordinary. It'll take some time to tell about this one, but hell - if it works, it's seriously neat.
On the one hand: This is potentially nice because it can be a pleasant interface to `personal assistant'-type software; a talking head that reminds you (in a friendly voice) about things you need to do, tries to predict your needs (electronic and otherwise) and acts as a data input source.
While streaming text etc. may be more efficient, most of the tasks a personal assistant needs to accomplish do not require rapid information transmission, but if anything an increased sense of personalization.
On the other hand: She searches around the web so that 'everyone's a journalist'? I thought that the point of a news service is that the data is collected by people that I trust to have common sense as to what is believable or not, and what is interesting or not. I simply do not believe that they have a computer capable of distinguishing such subtle layers of fact and fiction as is required to be a gateway between information sources and a news database.
And if indeed they did have such a computer, that (as their four-color glossy website claims) has its own tastes and enjoys electronica etc... why does that make me think `Sharon Apple?'
It seems like a potentially useful technology (real-time encoding of text into a talking head) being used in a potentially useless way. (Outputting the contents of a poorly-constructed news database)
There's actually been a lot of fuss about what's called "large extra dimensions" recently. The original problem was that the energy scale associated with gravity is about 10^19 GeV (1GeV = the energy an electron would get going through a potential gap of 10^9 V = approximately the mass of a proton) while the energy scale associated with all the other forces of nature is only 10^3 GeV. This is really bad because it means that (for instance) particles would get gravitational fields surrounding them that give them masses on the order of 10^19 GeV, which would turn everything in sight into a black hole.
This problem can be solved in a number of ways - notably supersymmetry, which causes those giant gravitational fields to cancel out. But there's one other odd problem to deal with, which are "extra dimensions." Basically string theory requires that the universe is actually 10-dimensional, and the other 6 dimensions are simply wrapped up very tightly. (Mental picture: If you wrap up a sheet of paper (which is 2-dimensional) into a very tight tube and look at it from far away, it looks 1-dimensional. Unless you're scanning it on distance scales comparable to the radius of the tube.) The problem is that you have to somehow wrap up these 6 dimensions on a really small distance scale (the length scale of gravity, about 10^-42 cm) and keep the other 4 really big. (the size of the universe) This again happens because the energy scale of gravity is big.
So about a year ago, Nima Arkani-Hamed, Savas Dimopoulos, Gia Dvali and John March-Russell had an interesting thought: We don't *know* that gravity really behaves like anything in particular at length scales below about a millimeter. (The current limit of experiment is about 0.8mm) So they noticed that the following setup gives the right answers too:
* We live in a universe with however many "extra" (small, rolled-up) dimensions, but these are rolled up with radii on the order of somewhere between 1fm (10^-15m, the size of a nucleus) to 0.1mm. (The range of sizes is because there are several different models)
* In this loosely rolled-up world, there are these 4-dimensional objects called "branes" floating around.
Then several amazing things happen. First of all, all matter particles (electrons, quarks, people) are bound to the surface of the brane and can't leave it. So are all the non-gravity force particles. (Photons, gluons, etc.) This just follows from the physical properties of branes in string theory, and it means that as far as anything but gravity is concerned, the universe is 4-dimensional and we won't see the extra dimensions.
Second, gravity completely ignores the brane (except insofar as there's matter, and therefore sources of gravity, there) and flies around freely in all of the dimensions. But because some of them are rolled up, what happens is that at long distances (bigger than the radius) all the gravity gets "squeezed" along the extra dimensions and gravity behaves like ordinary 4-dimensional gravity. At short distances, this changes -- for instance, the 1/r^2 force of gravity becomes something like 1/r^4.
But the real magic is, if the fundamental energy scale of gravity was 10^3 GeV, (the same as the scale for everything else) the distortion of gravity by the rolling up of space would make it seem like the scale was 10^19 GeV to any observer looking at distance scales bigger than the radius!
So the bonus of the Large Extra Dimensions (LED) scenario is, everything has the same energy scale, and it only seems that gravity has this high energy scale because we're looking at too long a distance. And all of the problems of a high energy scale indeed go away.
Of course, you can ask what the hell any of this has to do with reality. The thing is that all of this is consistent with all experiments to date and explains several tricky points. More importantly, it is experimentally testable; part of the testing happens in tabletop experiments (groups at Stanford and at NIST in Boulder are working on measuring gravity at distances down to about 10^-6 m) and part of it in accelerators. The final tests (thumbs up or thumbs down) will come from experiments at the LHC accelerator in Geneva, which should (knock on wood) be up to spin around 2004/5. Final results should take a few more years after the machine comes on-line.
But disclaimer: At this point this entire scenario is conjecture. People are already working out "observational experiments" to check these models -- for instance, whether these are consistent with the known spectrum of cosmic rays -- which are strong experimental constraints. But until the final experiments happen we can't be certain, one way or the other.
Also, since the original paper came out there have been several modified versions of the conjecture, which differ essentially in technical (but very important) points. The Randall-Sundrum model is especially important, and today's model looks to join the list of candidates.
So what does this mean for us? First of all, if it's right then the underlying scale of gravity is only 10^3 GeV, which is definitely accessible with the next generation (LHC) of accelerators. This means we can start to directly monkey around with the processes associated with black hole formation and the origins of the universe. Apart from completely changing physics (by making quantum gravity experiments practical) this is one of those things that creates more applications than we know what to do with. Making small black holes (and no, they wouldn't eat up the planet.:) is one thing. In some of the models effective FTL travel may be possible.
But possibly the most interesting thing is that there's no reason at all for our brane -- the one that our universe lives on -- is the only one. In fact, the most reasonable model suggests that there is some unbelievable number of branes floating out there, maybe 10^24 of them. It's not clear that the laws of physics would be the same on all of them -- e.g. the speed of light may be different, or the charge of the electron, or whatever -- but if the scenario turns out to be true, it is possible (though difficult) to communicate between two different worlds.
And for my money, that's the neatest thing of all.
Given an automatic scoring function for essays, it seems very natural for the enterprising young CS student to devise a genetic algorithm for composing papers. Fragments of sentences being bounced back and forth, run through a grammar checker and then passed to the essay grader... I wonder what this would produce?
Incidentally, does anybody know if the grading software is subject-specific, i.e. can evaluate that essay FOO is a good essay on Macbeth rather than a good essay on British colonialism?
As far as I can see, the primary weakness of this article is an insufficient differentiation between CBRN and Cyber attacks. The discussion of the restrictions and counterterrorist strategies is applicable almost only to CBRN, which has a high resource demand for its instigators and therefore is limited by their organizational structure. "Cyber" attacks work under substantially different parameters.
The first difference is in motivation. While a Cyber attack is potentially highly destructive (if the target were an infrastructure site rather than a propaganda site, as in the recent LTTE incident) the psychological impact of a disruption of services is much lower than that of a direct physical attack. A terrorist group attempting to sway a populace by fear would therefore not be as interested in such an attack unless they could carry out an extremely damaging one on a repeatable basis. (The threat of "we can do this anytime we want") Since it is possible to erect defenses around any Cyber target post facto, repeatable attacks are almost impossible without developing a new strategy every time; thus this sort of group is not a Cyber attack candidate.
The more serious candidate is a group attempting to generate a specific disruption as part of a more complex purpose, e.g. disruption of emergency response services in advance of a CBRN attack. This means that, although the Cyber attack has a very low organizational requirement, the motivation for one has the same requirement as a large Conventional/CBRN attack.
The other possible source is the accidental attack; if a "script kiddie" (a recreational pseudo-hacker using tools provided by a skilled hacker to gain access without a knowledge of the systems) were to somehow access an infrastructure system, they could cause substantial damage out of ignorance or malevolence. Such attacks are essentially unpredictable because there is virtually no needed organizational structure and a first-time incident may be damaging.
So several specific questions were posed as well:
The ease of bringing down vital systems depends strongly on the system. While it is possible to highly secure a system (e.g. the systems used for nuclear simulations at national labs are highly secure) this requires first of all taking the system off the net, and then posting physical and trustworthy guards around it. This is impractical in all but a few cases.
Anything less severe than this is always vulnerable in some sense; it is not possible to predict the full spectrum of possible attacks. The needed skill to do so may range from the minimal (vulnerable to 'script kiddies') to the very high (requires detailed technical knowledge) but in any case there are many people throughout the world with the requisite skills. Any security system must be based on the assumption that all electronic security is ultimately vulnerable.
The skills needed are essentially a deep knowledge of computer systems and a basic creativity. These skills are widespread and can be taught to anyone willing to experiment some and put in an effort; if anything, the silicon revolution was based on a whole culture of people with such skills. It is somewhat more difficult to learn penetration skills at the highest level, since people who know them are few and not famous for taking students; but anyone who can work up to the point where they're ready to learn more can teach themselves the rest.
COTS is a useful tool in CT, but all "standard procedures" fail in a domain as rapidly evolving as computers. Every security system has vulnerabilities which could be exploited, and even having skilled people constantly checking systems is not foolproof. A reliance on COTS on its own for security is foolhardy.
Any networked system is vulnerable.
Recovery can always be made; keep backups and so on. The serious issue is not recovery but the effects of the attack, e.g. disruption of critical infrastructure.
For an "overall recommendation" on Cyber terrorism, the points I would make are:
Any networked system is vulnerable; if a system is vulnerable and potentially a valuable target, it will be attacked. Some attacks will invariably penetrate defenses, and all defense systems must be built around this principle.
Systems should therefore be redundant and/or decentralized. It should not be possible to damage critical infrastructure by attacking a single target or multiple closely connected targets. This is probably the most important defensive point for Cyber warfare.
Hire hackers! This is already done to a fairly good extent, and it's sound policy. The same skills which can be used to mount attacks are the skills which design strong defenses. While COTS is intrinsically vulnerable, a skilled security person in command of a system can make a very large difference.
On that matter, sites with Cyber targets need to determine the security level which they desire and set and enforce policies which will create it. While this may seem trivial, very few places actually do this; most of them talk about security then institute policies with holes you could drive a Mack truck through.
That's my 2c... anyone feel that I'm totally off base?
Is it just me, or does it strike anyone as odd that uSquish claims to have fixed a code-level bug (as opposed to a bad config script) within a few hours?
IMHO, the only thing you could do for a security hole in that time is move it to another part of the code, and hope that you can actually fix it before someone else notices the problem. Does anyone know what Microsoft claims to have actually done?
No, there's reason to think they haven't made any super advances. There are simply too many people in the world thinking about factorization (it's an important problem for things other than cryptography) for someone to make a giant advance and nobody else to think of it. But all they need is exponentially larger calculational tools - and given maybe $50M you could build an amazing dedicated factorization machine.
A G4 would certainly be better than a G3, but its vector unit isn't in the same category as dedicated vector processors like in old-style Crays. An array of DSPs could be used creatively, though...
Not too much, unless it was a sufficiently large room. The big limiting step is diagonalizing a very large (about 6*10^6 for RSA-155) sparse matrix, and that just requires a single huge, preferably vector, processor. It's not usefully parallelizable, which can be a damned nuisance for a lot of other things in life.
* The 2GB of RAM needed to diagonalize the giant matrix just isn't quite as frightening and impressive as it was a couple of years ago...
* This algorithm is massively parallelizable...
... and it was done entirely in software. Small silicon units for the various subunits could quite easily be combined into a single machine, along with giant RAM banks with good shared memory access. This would not be horribly expensive on corporate or government scales.
Quick conclusion: If 512-bit numbers can be factored in 7 months of essentially downtime using software implementations on a parallel virtual machine, you can bet quite safely that much larger keys can be factored by several different groups who don't ordinarily write press releases about it.
Second thought: Which means that the brouhaha about exporting RSA is very likely a smokescreen to keep people thinking of it as a secure system.
Final thought: Given this, don't trust anything that needs to be really secure - defined as "anything someone who already has the financial resources needed to build a custom machine like this would want to know" to 512 bits, or 1024 bits. Or, most likely, 2048. Even assuming that "they" have no fundamental advances in number theory hidden away (which there's fair reason to believe) the keys we considered virtually impregnable a few years ago are now totally vulnerable.
So if we're agreed on keeping all the old keys, why not take this in the logical direction? We could save lots of hand motions if we add a couple of pedals to the computer, like on an organ. Want a few lines of boldface type? Instead of having to go to some damned menu, and either use the mouse or type alt-b [text] alt-b, just hold down pedal #1 while inputting...
And can you imagine what sort of EMACS key combinations you could put in? Escape-Meta-Alt-Control-Shift-Left Pedal-Stop 3-Bellows....
Something seems potentially dangerous here. A UV laser powerful enough to ionize a path of air might not slice straight through your cornea, but it's sure as hell not likely to be healthy.
A back-of-the envelope calculation: The beam has to ionize a path say about a micrometer on a side and about ten meters long. If a small current (so that we don't fry the guy at the other end of the Invisible Death Ray) isn't going to dissipate, we're going to need a conductivity of maybe 10^7 (Ohm-m)^-1. (like a metal) Conductivity is approximately n*q^2*t/m, where n is the charge carrier density, q is the charge of the carriers, t is the relaxation time (about 1.5ns; that's the decay time for the 2p state of Hydrogen) and m is the carrier mass. (About the electron mass, since air is an insulator) This means we're going to need a charge carrier density of about 2*10^23 per cubic meter, or a total of about 2*10^18 ions. Air is mostly nitrogen, which has a first ionization energy of 1400 kJ/mol, so the total amount of energy the laser would have to deliver is about 5 Joules. It would have to deliver this in about 10 microseconds (the time for light to travel the ten meters from the guy with the gun to the poor schmuck on the other end) so we need powers on the order of a megawatt for ten microseconds.
(End of calculation part) So practically? 5J in 10us is well above the level that can damage the eyeball even from indirect exposure. (Class IV) If the beam is UV, that makes it worse rather than better - the eye can absorb invisible light less than visible, and you can't see if you're accidentally going to zap yourself with it. So unless this calculation is off by a lot (several orders of magnitude) then I'm not sure how this beam isn't going to be a lot more dangerous than the makers intend. I'm getting kinda suspicious of their claims.
As the article pointed out, the huge bottleneck that the NSA (or anyone else) would have to solve in order to crack RSA for large key sizes is the ability to solve giant matrix equations quickly. We can probably guess that they haven't solved this part of the problem because that would lead to such extraordinary advances elsewhere - I'm thinking weapons and bomb development - that we'd be seeing much, much bigger and meaner things floating around out there if they had. Of course, you can still worry about quantum algorithms, which don't have a matrix-solving step... (Note to the paranoid: That was sarcasm. QC factorization algorithms are (a) not entirely proven - sources of noise, and possible very sneaky mathematical problems still may lurk and (b) not within twenty to fifty years at least of the capacities of any human technology.)
There's one really BFBI method thanks to the oddities of UNIX - delete/dev/dsp (or better, rename it and create a link so you don't have to muck around with mknod later) and rvplayer will mindlessly dump its output into a file where/dev/dsp was. Or if you want to be really snazzy, write a bit of code that creates a socket at/dev/dsp and real-time pipes it to your card...
Or better yet, why bother? Is there anything in RA that you really need to archive and play at high efficiency?
Slashdot Mirror
Absolutely - that's one of the reasons this is so exciting. As the other responder pointed out, this particle is weakly interacting and so we couldn't directly detect it, but it would show up as "missing energy". For instance, you could get a reaction at LHC on the lines of
proton + antiproton -> very energetic gluons -> squark + antisquark -> neutralinos + lots of other junk.
You could detect all of the other junk and measure its energy and momentum, and you'd see that there's a giant difference between that and the initial beam energy, so the difference must be particles that escaped your detection. Similarly you could measure the "missing charge" and so on, so you get a pretty good fix on what escaped.
The only catch is that 134GeV is actually about the absolute max that LHC will be able to see. The problem is that, while the interaction energy is about 2TeV (once everything's at full spin), the particles are protons and antiprotons. At these energies, you have to think of each of these as composite objects; bound states of three quarks (antiquarks) and a lot of gluons. The actual scattering is a quark off an antiquark, so each constituent particle has only about 1/7 of the total beam energy. On top of that, because of various conservation laws neutralinos (or any other SUSY particle) have to be created in pairs, so you need a lot of energy to do this.
But finding these particles (the buzzword is 'LSP,' Lightest Supersymmetric Particle) is one of the primary missions of LHC.
Yonatan
Several people seem interested in what dark matter is and whether its existence is a certain thing or a theory. So here's some stuff from the science end --
The matter you can actually see through a telescope is really only luminous matter; things which are directly emitting (a great deal of) light. Namely, stars, quasars, occasionally black holes (which are black but infalling matter creates huge X-ray jets) and things like that. Anything else, by definition, is "dark matter." (So by definition, you and I are made of dark matter - this is not generally that wierd a stuff)
The reason we know dark matter is there in large quantities is by measuring the motion of stars in galaxies and so on. Basically, we understand how gravity works pretty well (at least on astrophysical scales) and so by watching the motions and orbits of luminous objects, we can work backwards and find the distribution of mass in the universe. From this we find that only about 10% of all mass is luminous - the rest is "dark matter."
Now, it turns out we can find out substantially more about dark matter from these gravity measurements. (There are a lot of different kinds of measurements which I won't go into; suffice it to say that they all more or less agree) For one thing, we can tell how it clumps up, and from that deduce some things about its internal structure. For example, dark matter made out of heavy noninteracting particles (say about the mass of an iron nucleus) will move around very differently from dark matter made out of very light fast particles, which will move differently from large lumps of matter each about the size of a star, and so on.
The basic types of dark matter are:
Hot Dark Matter: (HDM) Small light particles moving about at close to the speed of light. Measurements suggest that there isn't much of this around, not enough to make a huge difference. Neutrinos would fall into this category.
Baryonic Cold Dark Matter: (Baryonic CDM) Heavy particles in the form of ordinary nuclei and atoms. Up to and including ourselves. This category also includes "MACHOs" (An acronym whose expansion I can't remember right now), which are essentially star-sized or bigger objects which we can't see. Brown dwarfs, large gas giants, and so on. Large dust clouds also fall into this category.
Non-Baryonic CDM: CDM means that the particles in question are heavy and so move much slower than the speed of light. Non-baryonic means that they're not made up of ordinary nuclei. This category includes what are called WIMPs (Weakly Interacting Massive Particles), which are any sort of big, heavy particle that doesn't interact much with other matter in the universe. (e.g., it can't have an electric charge, since that would make its dynamics very very unlike experimental data)
The reason WIMP searches are so cool is that any particle that turns out to be a WIMP will probably be very interesting in its own right. I can't explain all of the details in something of this length, but there is a symmetry called Supersymmetry (SUSY) which is postulated to exist. There are lots of good theoretical reasons to believe in it (for the technically minded: Grand unification doesn't work entirely right without SUSY, and you can't introduce fermions into string theories without SUSY.) and by now everyone is pretty much expecting to discover it experimentally soon; in fact, a discovery that SUSY doesn't exist would be even more interesting than a discovery that it does.
The reason I bring up this whole dreary story is that SUSY predicts that for every particle of ordinary matter (electrons, protons, photons, etc.) there is another related particle, its superpartner. A direct detection of a superpartner would be both a vivid confirmation of SUSY and incredibly useful experimental data about the structure and nature of the universe. (There are armies of physicists who are ready to strip every imaginable drop of information out of data right now. People have been waiting for this for a while.)
And lo and behold - the superpartner of the photon, called the neutralino, happens to have some properties that would make it a great candidate for a WIMP. It interacts very weakly indeed; for comparison, the Coulomb force between two electrons is proportional to 1/r^2, where r is their separation. The force between two neutralinos would scale something like e^(-r/r0)/r^2, where r0 is a characteristic distance on the order of perhaps 10^-20 meters. They're also stable - due to some conservation laws (analogous to conservation of electric charge, which makes circuits work) they can't decay into anything else, so once they're created, you're pretty much stuck with them drifting through the universe. And they're heavy - experimentally, their mass should be somewhere between 80-a few hundred GeV. (For comparison, a Hydrogen atom has a mass of just over 1GeV)
Now the Rome group is claiming to have detected WIMPs of masses somewhere between 52 and 134 GeV, which are candidates to be neutralinos. This will definitely spark some excitement and a lot of discussion. What happens next is that people are going to be reading this and arguing over every detail of their data analysis and so on, and other people will try to replicate their results. If this is confirmed, it represents a big step in understanding both the large-scale nature of the universe (WIMPs, and the nature and origin of dark matter) and its very small-scale structure. (SUSY, the fundamental interactions of matter)
OTOH, one shouldn't get too excited yet -- this represents an interesting result but it still has to go through a very rigorous checking and repeating process. It has happened (quite a few) times before that interesting signals have been observed which later turn out to be something very ordinary. It'll take some time to tell about this one, but hell - if it works, it's seriously neat.
Yonatan
On the one hand: This is potentially nice because it can be a pleasant interface to `personal assistant'-type software; a talking head that reminds you (in a friendly voice) about things you need to do, tries to predict your needs (electronic and otherwise) and acts as a data input source.
While streaming text etc. may be more efficient, most of the tasks a personal assistant needs to accomplish do not require rapid information transmission, but if anything an increased sense of personalization.
On the other hand: She searches around the web so that 'everyone's a journalist'? I thought that the point of a news service is that the data is collected by people that I trust to have common sense as to what is believable or not, and what is interesting or not. I simply do not believe that they have a computer capable of distinguishing such subtle layers of fact and fiction as is required to be a gateway between information sources and a news database.
And if indeed they did have such a computer, that (as their four-color glossy website claims) has its own tastes and enjoys electronica etc... why does that make me think `Sharon Apple?'
It seems like a potentially useful technology (real-time encoding of text into a talking head) being used in a potentially useless way. (Outputting the contents of a poorly-constructed news database)
Whoops... the original LED scenario was Arkani-Hamed, Dimopoulos and Dvali. Their original paper is here. Sorry!
Yonatan
Because it was last week?
You know, it's been a fairly odd day already...
There's actually been a lot of fuss about what's called "large extra dimensions" recently. The original problem was that the energy scale associated with gravity is about 10^19 GeV (1GeV = the energy an electron would get going through a potential gap of 10^9 V = approximately the mass of a proton) while the energy scale associated with all the other forces of nature is only 10^3 GeV. This is really bad because it means that (for instance) particles would get gravitational fields surrounding them that give them masses on the order of 10^19 GeV, which would turn everything in sight into a black hole.
:) is one thing. In some of the models effective FTL travel may be possible.
This problem can be solved in a number of ways - notably supersymmetry, which causes those giant gravitational fields to cancel out. But there's one other odd problem to deal with, which are "extra dimensions." Basically string theory requires that the universe is actually 10-dimensional, and the other 6 dimensions are simply wrapped up very tightly. (Mental picture: If you wrap up a sheet of paper (which is 2-dimensional) into a very tight tube and look at it from far away, it looks 1-dimensional. Unless you're scanning it on distance scales comparable to the radius of the tube.) The problem is that you have to somehow wrap up these 6 dimensions on a really small distance scale (the length scale of gravity, about 10^-42 cm) and keep the other 4 really big. (the size of the universe) This again happens because the energy scale of gravity is big.
So about a year ago, Nima Arkani-Hamed, Savas Dimopoulos, Gia Dvali and John March-Russell had an interesting thought: We don't *know* that gravity really behaves like anything in particular at length scales below about a millimeter. (The current limit of experiment is about 0.8mm) So they noticed that the following setup gives the right answers too:
* We live in a universe with however many "extra" (small, rolled-up) dimensions, but these are rolled up with radii on the order of somewhere between 1fm (10^-15m, the size of a nucleus) to 0.1mm. (The range of sizes is because there are several different models)
* In this loosely rolled-up world, there are these 4-dimensional objects called "branes" floating around.
Then several amazing things happen. First of all, all matter particles (electrons, quarks, people) are bound to the surface of the brane and can't leave it. So are all the non-gravity force particles. (Photons, gluons, etc.) This just follows from the physical properties of branes in string theory, and it means that as far as anything but gravity is concerned, the universe is 4-dimensional and we won't see the extra dimensions.
Second, gravity completely ignores the brane (except insofar as there's matter, and therefore sources of gravity, there) and flies around freely in all of the dimensions. But because some of them are rolled up, what happens is that at long distances (bigger than the radius) all the gravity gets "squeezed" along the extra dimensions and gravity behaves like ordinary 4-dimensional gravity. At short distances, this changes -- for instance, the 1/r^2 force of gravity becomes something like 1/r^4.
But the real magic is, if the fundamental energy scale of gravity was 10^3 GeV, (the same as the scale for everything else) the distortion of gravity by the rolling up of space would make it seem like the scale was 10^19 GeV to any observer looking at distance scales bigger than the radius!
So the bonus of the Large Extra Dimensions (LED) scenario is, everything has the same energy scale, and it only seems that gravity has this high energy scale because we're looking at too long a distance. And all of the problems of a high energy scale indeed go away.
Of course, you can ask what the hell any of this has to do with reality. The thing is that all of this is consistent with all experiments to date and explains several tricky points. More importantly, it is experimentally testable; part of the testing happens in tabletop experiments (groups at Stanford and at NIST in Boulder are working on measuring gravity at distances down to about 10^-6 m) and part of it in accelerators. The final tests (thumbs up or thumbs down) will come from experiments at the LHC accelerator in Geneva, which should (knock on wood) be up to spin around 2004/5. Final results should take a few more years after the machine comes on-line.
But disclaimer: At this point this entire scenario is conjecture. People are already working out "observational experiments" to check these models -- for instance, whether these are consistent with the known spectrum of cosmic rays -- which are strong experimental constraints. But until the final experiments happen we can't be certain, one way or the other.
Also, since the original paper came out there have been several modified versions of the conjecture, which differ essentially in technical (but very important) points. The Randall-Sundrum model is especially important, and today's model looks to join the list of candidates.
So what does this mean for us? First of all, if it's right then the underlying scale of gravity is only 10^3 GeV, which is definitely accessible with the next generation (LHC) of accelerators. This means we can start to directly monkey around with the processes associated with black hole formation and the origins of the universe. Apart from completely changing physics (by making quantum gravity experiments practical) this is one of those things that creates more applications than we know what to do with. Making small black holes (and no, they wouldn't eat up the planet.
But possibly the most interesting thing is that there's no reason at all for our brane -- the one that our universe lives on -- is the only one. In fact, the most reasonable model suggests that there is some unbelievable number of branes floating out there, maybe 10^24 of them. It's not clear that the laws of physics would be the same on all of them -- e.g. the speed of light may be different, or the charge of the electron, or whatever -- but if the scenario turns out to be true, it is possible (though difficult) to communicate between two different worlds.
And for my money, that's the neatest thing of all.
Didn't it occur to anyone to get a copy of MS*, make a bunch of copies, then turn them in for real ones?
Given an automatic scoring function for essays, it seems very natural for the enterprising young CS student to devise a genetic algorithm for composing papers. Fragments of sentences being bounced back and forth, run through a grammar checker and then passed to the essay grader... I wonder what this would produce?
Incidentally, does anybody know if the grading software is subject-specific, i.e. can evaluate that essay FOO is a good essay on Macbeth rather than a good essay on British colonialism?
Yonatan
The first difference is in motivation. While a Cyber attack is potentially highly destructive (if the target were an infrastructure site rather than a propaganda site, as in the recent LTTE incident) the psychological impact of a disruption of services is much lower than that of a direct physical attack. A terrorist group attempting to sway a populace by fear would therefore not be as interested in such an attack unless they could carry out an extremely damaging one on a repeatable basis. (The threat of "we can do this anytime we want") Since it is possible to erect defenses around any Cyber target post facto, repeatable attacks are almost impossible without developing a new strategy every time; thus this sort of group is not a Cyber attack candidate.
The more serious candidate is a group attempting to generate a specific disruption as part of a more complex purpose, e.g. disruption of emergency response services in advance of a CBRN attack. This means that, although the Cyber attack has a very low organizational requirement, the motivation for one has the same requirement as a large Conventional/CBRN attack.
The other possible source is the accidental attack; if a "script kiddie" (a recreational pseudo-hacker using tools provided by a skilled hacker to gain access without a knowledge of the systems) were to somehow access an infrastructure system, they could cause substantial damage out of ignorance or malevolence. Such attacks are essentially unpredictable because there is virtually no needed organizational structure and a first-time incident may be damaging.
So several specific questions were posed as well:
Anything less severe than this is always vulnerable in some sense; it is not possible to predict the full spectrum of possible attacks. The needed skill to do so may range from the minimal (vulnerable to 'script kiddies') to the very high (requires detailed technical knowledge) but in any case there are many people throughout the world with the requisite skills. Any security system must be based on the assumption that all electronic security is ultimately vulnerable.
For an "overall recommendation" on Cyber terrorism, the points I would make are:
That's my 2c... anyone feel that I'm totally off base?
Is it just me, or does it strike anyone as odd that uSquish claims to have fixed a code-level bug (as opposed to a bad config script) within a few hours?
IMHO, the only thing you could do for a security hole in that time is move it to another part of the code, and hope that you can actually fix it before someone else notices the problem. Does anyone know what Microsoft claims to have actually done?
No, there's reason to think they haven't made any super advances. There are simply too many people in the world thinking about factorization (it's an important problem for things other than cryptography) for someone to make a giant advance and nobody else to think of it. But all they need is exponentially larger calculational tools - and given maybe $50M you could build an amazing dedicated factorization machine.
A G4 would certainly be better than a G3, but its vector unit isn't in the same category as dedicated vector processors like in old-style Crays. An array of DSPs could be used creatively, though...
Not too much, unless it was a sufficiently large room. The big limiting step is diagonalizing a very large (about 6*10^6 for RSA-155) sparse matrix, and that just requires a single huge, preferably vector, processor. It's not usefully parallelizable, which can be a damned nuisance for a lot of other things in life.
Some things to ponder while reading this:
* The 2GB of RAM needed to diagonalize the giant matrix just isn't quite as frightening and impressive as it was a couple of years ago...
* This algorithm is massively parallelizable...
... and it was done entirely in software. Small silicon units for the various subunits could quite easily be combined into a single machine, along with giant RAM banks with good shared memory access. This would not be horribly expensive on corporate or government scales.
Quick conclusion: If 512-bit numbers can be factored in 7 months of essentially downtime using software implementations on a parallel virtual machine, you can bet quite safely that much larger keys can be factored by several different groups who don't ordinarily write press releases about it.
Second thought: Which means that the brouhaha about exporting RSA is very likely a smokescreen to keep people thinking of it as a secure system.
Final thought: Given this, don't trust anything that needs to be really secure - defined as "anything someone who already has the financial resources needed to build a custom machine like this would want to know" to 512 bits, or 1024 bits. Or, most likely, 2048. Even assuming that "they" have no fundamental advances in number theory hidden away (which there's fair reason to believe) the keys we considered virtually impregnable a few years ago are now totally vulnerable.
aack...
So if we're agreed on keeping all the old keys, why not take this in the logical direction? We could save lots of hand motions if we add a couple of pedals to the computer, like on an organ. Want a few lines of boldface type? Instead of having to go to some damned menu, and either use the mouse or type alt-b [text] alt-b, just hold down pedal #1 while inputting...
And can you imagine what sort of EMACS key combinations you could put in? Escape-Meta-Alt-Control-Shift-Left Pedal-Stop 3-Bellows....
A back-of-the envelope calculation: The beam has to ionize a path say about a micrometer on a side and about ten meters long. If a small current (so that we don't fry the guy at the other end of the Invisible Death Ray) isn't going to dissipate, we're going to need a conductivity of maybe 10^7 (Ohm-m)^-1. (like a metal) Conductivity is approximately n*q^2*t/m, where n is the charge carrier density, q is the charge of the carriers, t is the relaxation time (about 1.5ns; that's the decay time for the 2p state of Hydrogen) and m is the carrier mass. (About the electron mass, since air is an insulator) This means we're going to need a charge carrier density of about 2*10^23 per cubic meter, or a total of about 2*10^18 ions. Air is mostly nitrogen, which has a first ionization energy of 1400 kJ/mol, so the total amount of energy the laser would have to deliver is about 5 Joules. It would have to deliver this in about 10 microseconds (the time for light to travel the ten meters from the guy with the gun to the poor schmuck on the other end) so we need powers on the order of a megawatt for ten microseconds.
(End of calculation part) So practically? 5J in 10us is well above the level that can damage the eyeball even from indirect exposure. (Class IV) If the beam is UV, that makes it worse rather than better - the eye can absorb invisible light less than visible, and you can't see if you're accidentally going to zap yourself with it. So unless this calculation is off by a lot (several orders of magnitude) then I'm not sure how this beam isn't going to be a lot more dangerous than the makers intend. I'm getting kinda suspicious of their claims.
Given Intel's infamous chip-temperature record, I'm not sure I'd want a 600MHz chip in anything that's going to be on my lap...
As the article pointed out, the huge bottleneck that the NSA (or anyone else) would have to solve in order to crack RSA for large key sizes is the ability to solve giant matrix equations quickly. We can probably guess that they haven't solved this part of the problem because that would lead to such extraordinary advances elsewhere - I'm thinking weapons and bomb development - that we'd be seeing much, much bigger and meaner things floating around out there if they had. Of course, you can still worry about quantum algorithms, which don't have a matrix-solving step... (Note to the paranoid: That was sarcasm. QC factorization algorithms are (a) not entirely proven - sources of noise, and possible very sneaky mathematical problems still may lurk and (b) not within twenty to fifty years at least of the capacities of any human technology.)
"C2 without a network"?! Somehow I wouldn't want to put that on my four-color glossies... do businesses even think about this before they buy it?
Sheesh.
There's one really BFBI method thanks to the oddities of UNIX - delete /dev/dsp (or better, rename it and create a link so you don't have to muck around with mknod later) and rvplayer will mindlessly dump its output into a file where /dev/dsp was. Or if you want to be really snazzy, write a bit of code that creates a socket at /dev/dsp and real-time pipes it to your card...
Or better yet, why bother? Is there anything in RA that you really need to archive and play at high efficiency?