Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. ×

Comment Re:Practical? (Score 1) 140

I fully understand that but using the brute force attack does provide a good metric by how to judge things and yes I know that in my previous statement I didn't cover more detailed attacks as no one would like to read that wall of text. In response to another user above I look a little more closely at AES-256 taking into account using a quantum computer and the best attack against it. In that case we move from stellar mass energy requirements down to something that would become fairly trivial with a complexity of about 2^50.

Comment Re:Practical? (Score 1) 140

If losing encryption keys is going to be a problem for with crypto that strong then it is already a problem for you as you neither have an ideal classical computer operating near the limit of Landauer's Principal nor do you have the ability to consume a large fraction of the US's total annual energy consumption. The problem is with encryption is that if it is feasable for a state actor to crack it, then it is also possiable for a large criminal gang to do so in a few years, and a few years later you can do so with a device that runs on a battery that you carry in your pocket, see the image in the original article where they point out that generating MD5 hash collisions can be done on your smart phone in about 30 seconds.

Comment Re:Practical? (Score 1) 140

The reason I want crypto that has a chance of surviving the heat death of the universe is simple. Unless you are using a One Time Pad the encryption you haven't isn't provably secure for all time. It will be attacked and the strength of it will decrease. Is my data so important that it personally needs to be kept secure until the heat death of the universe? Simple answer is no, but at the same time it is something that I would like to see stay secure for the next 50-60 years until I'm taking a dirt nap.

So now lets look at AES-256. Here we are dealing with a cipher that is in that mass energy of a star to brute force on an ideal classical computer. Now that may seem pretty damn strong, but there is a related key attack against it that brings that complexity down to 2^99.5 from 2^256. At this point we are no longer talking about star sized energy requirements but instead a sizeable portion of the total annual energy output of a a nation on an ideal classical computer. While currently infeasible further advances in cryptanalysis and quantum computing will decrease this further. So using something like Grover's algorithm we could possibly get the work down to about 2^50. At that level we have already rejected crypto standards because they are easy to defeat.

Comment Re:Practical? (Score 5, Informative) 140

Ever since I read this blurb from Applied Cryptography by Bruce Schneier years ago it has really put things into perspective when it comes to what is strong crypto and what isn't. I got the concept from him so it isn't my own idea even if I did simplify the explanation of it.:

One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a single bit by changing the state of a system requires an amount of energy no less than kT, where T is the absolute temperature of the system and k is the Boltzman constant. (Stick with me; the physics lesson is almost over.)

Given that k = 1.38×10^-16 erg/Kelvin, and that the ambient temperature of the universe is 3.2 Kelvin, an ideal computer running at 3.2K would consume 4.4×10^-16 ergs every time it set or cleared a bit. To run a computer any colder than the cosmic background radiation would require extra energy to run a heat pump.

Now, the annual energy output of our sun is about 1.21×10^41 ergs. This is enough to power about 2.7×10^56 single bit changes on our ideal computer; enough state changes to put a 187-bit counter through all its values. If we built a Dyson sphere around the sun and captured all its energy for 32 years, without any loss, we could power a computer to count up to 2^192. Of course, it wouldn't have the energy left over to perform any useful calculations with this counter.

But that's just one star, and a measly one at that. A typical supernova releases something like 10^51 ergs. (About a hundred times as much energy would be released in the form of neutrinos, but let them go for now.) If all of this energy could be channeled into a single orgy of computation, a 219-bit counter could be cycled through all of its states.

These numbers have nothing to do with the technology of the devices; they are the maximums that thermodynamics will allow. And they strongly imply that brute-force attacks against 256-bit keys will be infeasible until computers are built from something other than matter and occupy something other than space.

I want crypto that has a good chance of outlasting the heat death of the universe even with a quantum computer. For symmetric key crypto this means you would need somewhere around a 601 bit keyspace IIRC before you exceed the mass energy of the universe.

Comment Re:Practical? (Score 1) 140

Sounds very practical to me. The fact that this is in the realm of being done by a wealthy individual should indicate why. Lets say you are a wealthy criminal gang go out and get your self a bunch of beefy servers and fill them with GPUs. You now can defraud banks and others at a massive scale and probably make the money back in short order. 6500 CPUs and 110 GPUs isn't all that expensive. You could probably get that for $10,000,000-$20,000,000 and next year it will cost even less to get that computational power. The fact that we aren't talking about time or energy requirements that are on the order of lifetimes of stars or the mass energy of a star should tell you that it broken. Also attacks only get better with time. It only took 4 years to go from theoretical to actual.

Comment Re:Radiation? (Score 1) 273

As AC said, not necessarily for things evolved to survive in it. Tardigrades for example can handle fairly large doses just fine.

The planets are also likely tidally locked, and solar radiation would be a complete non-issue for anything on the dark side of the planet. Life has no need for light after all, it had been thriving on Earth for millions of years before the first bacteria evolved a light-sensitive protein that let them detect daylight and flee to deeper, safer water. And many millions of years more before one evolved the ability to harness light for energy.

Comment Re:What makes this special? (Score 1) 273

We're talking about space science - "someday" is usually presumed to be many decades or centuries in the future.

And is that all? Really? That's not too bad. Child's play once we get serious about astronomy and start building gravitational telescopes using our sun as the lens. What could you resolve with a 550-700AU focal length?

Comment Re:Sterile and shattered. Or Not (Score 1) 273

No, rotation isn't required for tidal forces, just for those forces to substantially "massage" a planet. Just squeezing the planet doesn't add heat, the squeeze needs to be changing to generate substantial heat.

It's true you'll still get some tidal effects due to eccentricity, but they'll be far smaller than if the planet was rotating - if you imagine the tides squeezing a stress-ball into more of a football shape, rotation means the bulges are traveling around the planet once per day. Without rotation you'll get just a slight change in how tight you're squeezing as the planet move closer and further from its primary, as well as some very slight oscillation of the bulge across the surface due to the associated libration.

I suppose though if we're talking about tight orbits around a huge primary, even a tiny fraction of the original tidal effects could still be quite large.

Hmm, and there will be another effect as well - that of the pulsating "tides" from the other planets - after all the distance between their orbits ranges between only about 2x and 4x that between the Earth and Moon, except for the outermost at ~6x the distance. That would be a factor with Jupiter's moons as well. I wonder how the magnitude of the effect would compare?

Slashdot Top Deals

"There... I've run rings 'round you logically" -- Monty Python's Flying Circus

Working...