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

 



Forgot your password?
typodupeerror

Comment Re:Enigma (Score 1) 128

Obviously, you do not understand how enigma works. With 20 wheels you have an 26^20 initial configuration and defining thousands of wheel turning patters makes the attacker's work much-much harder.

And actually, cracking the original enigma should takes just a few seconds on today's desktop computers.

Enigma basically replaces each letter with a different one according to the wheel settings. With 20 wheels the initial configuration contains 20 characters plus the number of the wheel turning pattern. This is far stronger than a simple one-time pad with 20 characters (aka 20*5 bits = 100 bits).

Also, a wheel can contain the whole ASCII table in which case the initial configuration is 255^20.

Comment Enigma (Score 2) 128

Just create a software version of Enigma (https://en.wikipedia.org/wiki/Enigma_machine) with eg. 20 wheels. Also, create a matrix which contains how the wheels should turn. You can create thousands of wheel turning patters. Voila, unbreakable encryption without using a sufficiently long one time pad.

Of course, the initial configuration has to be sent somehow (eg. via courier or other conventional ways which 3-letter agencies seem to forget) and the encoding/decoding machine should never be connected to the internet.

Comment Re:TL;DR (Score 1) 189

No, I invoked the gambler's fallacy because it seemed to me that the original poster assumed that the system has memory.

It is stated in wikipedia:
Gambler's fallacy does not apply when the probability of different events is not independent...

Since I consider different rocket launch as independent events I think gambler's fallacy applies to some extent.

So, the only way to calculate a success rate of a launch if you get the failure rate of every component of the rocket and do some calculations based on those. However, calculating the success of the 9th mission after the success of the previous 8 or before even the first one has no physical meaning. Maybe it has some kind of theoretical one which has no connection to the physical world.

Comment Re:TL;DR (Score 1) 189

>We have no missions. What is the chance that we get 9 missions coming back alive? (1/2)^9 = 0.001953125 = 0.2%.

This is true if you have a fair coin as in the Gambler's fallacy example. However, I do not believe a rocket can be treated as a fair coin. First of all you have to change the coin for every toss and these coins have to be imperfect. This will totally screw up a simple probability calculation.

In reality, if you go down to the quantum level you can say that the quantum state of each rocket will be totally different and in this way calculating the probability of the 9th mission before the first one will have absolutely no meaning.

Comment Properties of spacetime (Score 1) 274

What about if spacetime itself has some properies? Eg. tension? At relatively short distances the curvature of spacetime diminishes with r^2. However, as we go further and further from the center of the curvature, spacetime reaches flatness slower and slower. This can explain the galaxy rotation problem and other phenomena which requires dark matter.

This is similar to what MOND tries to achive, but unfotunately MOND does not say anything about spacetime.

Comment Why gravity is treated as a force? (Score 1) 97

Why do physicists insist on treating gravity as a force? Since Einstein, we know gravity is the curvature of space-time. It may be represented as a force in calculations but in reality there is no force.

If gravity is not a force then do we really have a hierarchy problem? For eg. shouldn't Newton's constant, G, be some kind of average curvature of space-time between two bodies and be calculable from this curvature?

Obviously, if this is the case, G has nothing to do with Fermi's constant and we should not compare the two.

Submission + - Slashdot BETA Discussion (slashdot.org) 60

mugnyte writes: With Slashdot's recent restyled "BETA" slowly rolled to most users, there's been a lot of griping about the changes. This is nothing new, as past style changes have had similar effects. However, this pass there are significant usability changes: A narrower read pane, limited moderation filtering, and several color/size/font adjustments. BETA implies not yet complete, so taking that cue — please list your specific, detailed opinoins, one per comment, and let's use the best part of slashdot (the moderation system) to raise the attention to these. Change can be jarring, but let's focus on the true usability differences with the new style.

Slashdot Top Deals

Nothing in progression can rest on its original plan. We may as well think of rocking a grown man in the cradle of an infant. -- Edmund Burke

Working...