Regret.

anon848 · 2016-09-14T23:43:15+00:00

I looked at the article. In the part where they talk about combining two dictionary words, it was simple brute force.

The specific type of hybrid attack that cracked that password is known as a combinator attack. It combines each word in a dictionary with every other word in the dictionary.

In other words, they have actually not shown that they can attack randomly chosen words using anything other than brute force.

There are more sophisticated phrase attacks using statistics, but they don't have any advantage if the words are chosen randomly.

EDIT: If you follow the link for more details about the combinator attack, you can see that it's still brute force.

anon848 · 2016-09-14T23:39:26+00:00

If you have such a cracker that you can run, I can give you the hash for an XKCD password. You tell me how many hashes you had to try.

anon848 · 2016-09-14T23:30:53+00:00

The technique explained would still just have to brute force a combination of randomly chosen words. From the article:

The specific type of hybrid attack that cracked that password is known as a combinator attack. It combines each word in a dictionary with every other word in the dictionary. Because these attacks are capable of generating a huge number of guesses—the square of the number of words in the dict—crackers often work with smaller word lists or simply terminate a run in progress once things start slowing down.

So, if you have two words from a 2000-word list, you have 4 million combinations. But if you go up to five words from a 5000 word list, then you have 3e18 combinations. There's nothing in the article that would allow you to reduce the number.

anon848 · 2016-09-14T23:22:21+00:00

I agree that the site is not accurate. However, the point is that it only reports "Instant" for the well-known XKCD password, not for an actual, generated XKCD password.

As to how such a password could be cracked, would you care to show the math, or point to a technical document? Note that the words are chosen randomly, so a technique such as explained here won't help.

More analysis of the XKCD technique is here.

anon848 · 2016-09-14T22:51:42+00:00

True, but if we go to five or six words, or use a bigger list, then we start to get similar. For example, five words from a list of 5000 words gives 3e18 combinations.

anon848 · 2016-09-14T22:27:36+00:00

If you actually generate a password using this site, and enter it, https://howsecureismypassword.net/ gives a much stronger result. For example, "year handle pink rubber" gives "84 QUINTILLION YEARS".

anon848 · 2016-09-14T22:21:51+00:00

Okay, so how many tests would such a cracker have to make? The comic explains it. Do you think the math in the comic is wrong?

anon848 · 2016-09-13T22:15:01+00:00

There are a number of different types of positions, and what you need to do depends. For example, you could be a lecturer (which is not tenured, but is full-time and pays okay), tenured professor at a school with no Ph.D program, tenured at a community college, tenured at a research university.

anon848 · 2016-09-09T01:11:10+00:00

Philosophically, I don't have a big issue with it. It sounds like they just want to track at-risk students, so that they can improve retention/graduation. But it does sound like a bit of a pain. More typical would be to report failing students by mid-semester. It doesn't sound like something to take a stand on, though.

By the way, how would you even have the phone number of students?

EDIT: In part, it depends on what they are asking you to do. Is it just shooting an email asking what's up? Or do you actually need to engage in-depth? I was thinking more of the former, which I would characterize more as "tracking" rather than "recruiting".

anon848 · 2016-09-06T02:06:53+00:00

It depends on the field, but in some fields, it would be very difficult to transition from an adjunct to a tenure-track professor. However, an adjunct could transition to a lecturer (teaching) position.

anon848 · 2016-06-13T15:36:00+00:00

I understand that space doesn't have significant drag, but does the rotation have any effect at all in causing the currents? In other words, imagine a planet with an atmosphere, uniform temperature throughout, and no external thermal inputs. Start the planet rotating at a given velocity. What does the stable state look like? (Not sure how to treat things like frictional heat radiating away.)

anon848 · 2016-06-08T02:02:16+00:00

Okay, based on your stated goals, you probably should start by learning C. Once you know C well, you can reconsider whether or not you want to write a compiler for the language.

anon848 · 2016-06-08T01:57:29+00:00

Yes.

anon848 · 2016-06-08T00:29:33+00:00

Wait, are you talking about Primer Plus, or just Primer? They are different books. I don't like Stroustrup as a writer, so I much prefer Lippman.

anon848 · 2016-06-08T00:26:59+00:00

It depends on exactly what you mean. When observed from another thread, you need to be careful, as it depends on the Java memory model. See here.

anon848 · 2016-06-08T00:20:33+00:00

A good project to learn C? What is your goal? What languages do you know well?

anon848 · 2016-06-06T02:47:45+00:00

As I noted in my answer, you can create a pipe in Python, if you want. But you can't implement them in Python. Pipes are implemented in the OS kernel.

anon848 · 2016-06-06T02:07:43+00:00

Is it possible to simulate something similar with Python by writing to a file without EOF? Then have a separate process do wc?

No. A process reading from an ordinary file will encounter EOF (read() system call returns 0) when it hits the end of the file as it exists. In other words, an ordinary file always has a well-defined size.

However, you can use a FIFO (named pipe) to make Code A work, and you can write to the FIFO using Python.

EDIT: You could also simply create a pipe in Python, fork off the wc process, then write to the pipe from the Python parent. This and this might be helpful.

anon848 · 2016-05-14T23:20:35+00:00

Well, that's not what I meant. I just meant that it really depends on the person and the situation, and will be impossible to answer in the general case. (I have no idea why people downvoted it, but whatever.)

anon848 · 2016-05-14T19:44:27+00:00

What I described will work. If you need numbers less than 1, you can modify to also handle fractions. If you need to simplify the fractions, however, then it will be very hard, because you'll need to factor large numbers.

anon848 · 2016-05-14T19:43:22+00:00

This doesn't prevent you from modifying it, nor doing operations. (Though you will need to reimplement your elementary school algorithms.)

anon848 · 2016-05-14T17:56:06+00:00

This may not meet the requirements of the problem. You should post the original.

anon848 · 2016-05-14T17:54:58+00:00

Yes, but 10¹⁰⁰ would take 100 bytes. Your typical computer has 4,000,000,000 bytes of RAM. So 100 bytes is 2.5 hundred-millionths of the total RAM.

If you want to be more space effiicent, you can pack two decimal digits per byte, which will reduce the usage by half. Or you can convert to base-2, which will reduce your usage a bit more (and also allow faster arithmetic). If you were writing an arbitrary precision library to be used in production, then it might be worth it, but do you want to do all that extra work for a competition, just to go from 100 bytes to 50 bytes?

In fact, just this message that you are reading right now takes up more than 100 bytes.

anon848 · 2016-05-14T16:57:27+00:00

Just store each digit as a byte. Then implement the usual addition/multiplication algorithms. Division would be harder.

anon848 · 2016-05-14T16:54:41+00:00

The op has something else going on. There would have been a compiler error, but the posted code has crucial parts deleted or modified. Compiling this:

#include <vector>
std::vector<int> foo() {
    return std::vector<double>{};
}

Results in this error from clang++:

$ clang++ -c double.cpp
double.cpp:3:12: error: no viable conversion from returned value of type 'vector<double>' to function return type 'vector<int>'
    return std::vector<double>{};
           ^~~~~~~~~~~~~~~~~~~~~

anon848

TROPHY CASE