Wikipedia:Reference desk/Archives/Computing/2006 July 30

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Security of ZIP files

I've heard that just about any method of cryptography is crackable someway or another. What i need to know is just how secure is the encryption of of ZIP files. specifically, by using the "Compressed (zipped) Folder" feature in XP and using "Add Password" from the context menu.

Lets say i had some realy sensitive data to store...

Is there ANY WAY to crack or bypass the encryption? would it be feasable on a high-end consumer desktop? What if it landed in the hands of some intelligence agency? can they crack it?

not done yet, a few more questions...

If the attacker does NOT use a brute force attack (trying the possibilities sequentially), is it any more secure to use a long and complex password? what if he DOES try brute force, would using an 8-digit pin be signifcantly less secure than using a long random or pseudo-random alphanumeric (and is there a limit to the length)?

Now lets say it is crackable, what kind of resources? again.. can it be done on a consumer desktop?.. what if its handed over to an expert or security company to try cracking it?

Finally, if it is a weak method to secur my data, what are some other alternatives that are quick and easy (that is, drag-and-drop into the "secure" archive/folder)

Thanks in advance if you can answer some of these questions. I already checked out some of the cryptography articles and the ZIP format article, but if you have external links regarding this specific scenario, please do post them. 02:55, 30 July 2006 (UTC)

One easy way to know about this is to try and search for utilities that remove passwords. All of the ones on the web that I found use brute-force methods, which means that a very long password made up of random letters and numbers (i.e. not something that would be subjected to a dictionary attack) would take a very, very long time to undo by brute force alone. Of course, it might also make it impossible for you to remember without writing down, and if someone found where you wrote it down...

Now, that aside, our article on ZIP (file format) says that "ZIP supports a simple password based symmetric encryption system which is known to be seriously flawed. In particular it is vulnerable to known-plaintext attacks which are in some cases made worse by poor implementations of random number generators". I don't know what that means in terms of practicality, but it should be worrisome if you are desperately concerned about the security of the data.

My recommendation: get a client (I am sure there are many out there) that can encrypt files themselves with something strong, like PGP, and use it to encrypt your ZIP files. --Fastfission 14:43, 30 July 2006 (UTC)

Please confirm how you want to do the encryption. You are using Windows XP and your hard drive uses NTFS. You right click on the folder, then pick properties. In the Properties menu that appears, you click the Advanced button. In the Advanced Attributes menu that appears, you see the boxes for "Compress contents to save disk space" and "Encrypt contents to secure data". You will find that you can only check one or the other. Is this what you mean? --Gerry Ashton 00:36, 31 July 2006 (UTC)

Largest (dot-com) corporations outside U.S. or in Singapore

1. What are the largest dot-com corporations outside the U.S.?
2. What are the largest corporations in Singapore?
3. What are the largest corporations in Singapore in the computing/IT industries, particularly dot-coms?

Here, size is defined both by revenue and how famous the corporation is.

--J.L.W.S. The Special One 07:22, 30 July 2006 (UTC)

Converting "CHM" Files to another format.

How can I convert ".chm" files ( I think compiled html files ) to some other format like pdf format?

Searching for "chm to pdf" on google returns a very large number of results. You didn't specify your operating system, so you'll have to search on your own. You may also consider converting chm to html then using a html to pdf converter. digfarenough (talk) 15:22, 30 July 2006 (UTC)

I would assume Windows, as the format seems to be most commonly used for help files. Are there other common uses for CHMs? --Optichan 16:41, 4 August 2006 (UTC)

Rigistry Error

I'm using WinXP Professionl without any service packs.Last time when I turned my PC to on,it loaded and displayed as usually the logo screen and showed immediatly that the Registry hive has been damaged and it can't be loaded.Rigistry Hive loading failed and some other info have been displayed..It was displyed in a Non-GUI Blue Screen and my computer freezed therby.I retried again and again by restarting but it was the ultimate....Then I had to repair using the Windows CD from the booting menu and so far but finally it re-installed the system files alone and hence I was able to recover my data..What's this problem all about and ofcourse I didn't reset the PC at all.I shutdown properly...But last time since I opened too many programs,windows said it was increasing my Virtual memory...but after few restarts,it finally displayed this error..Any precaution available?...and what's the cause?..

Get a spell-check. Get more RAM. Also, reformat your hard drive (full reformat) and reinstall Windows. Then update to service pack 2. Come back when you've done that, though this sounds really fake since if your PC failed, you couldn't post that question to wikipedia.--Frenchman113 on wheels! 15:36, 30 July 2006 (UTC)

The poster seemed to pretty clearly indicate that he/she was able to get Windows going again. Also, most people I know have access to more than one computer. Finally, "Then update to service pack 2" is a sentence fragment, consider getting a grammar-check. digfarenough (talk) 23:50, 30 July 2006 (UTC)

It's not a sentence fragment. Then is an adverb and update is in the imperative. Perhaps I should have used a comma though.--Frenchman113 on wheels! 17:33, 31 July 2006 (UTC)

Whoaaaa buddy, i dont want to be just busting on XP because we're kind of stuck with it, but it is insecure and full of bugs with all the latest service packs and patches, using the original release without updates is asking for troulbe. go to www.windowsupdate.com 02:41, 1 August 2006 (UTC)

java

Tulika 99 16:15, 30 July 2006 (UTC) halow!! iv written a really long program.....it dosnt hav ne syntax errors. its thru input stream reader.....but im not being able 2 access 2 the window wer i have 2 enter all the variables. its gives me a list of object clone() boolean equals(object) void finalize().....

i donno what to do ahead... can u plzz hepl me out thnks!!!!

Just because a program does not have syntax errors does not mean it does not have errors. Because you wrote a "long" program, the chance of finding the error is going to be very small. However, fill your program with as many System.out.println("I am at section FILL IN THE NAME OF THE SECTION AND WHAT IT IS DOING HERE"); statements as you can. You will see where it is quitting. Also, if your programming is as pathetic as your spelling, you are going have a great difficulty in getting anything to run as you like. It isn't just being mean or anal. If you can't take the time to write a word like "any" and need to abbreviate it as "ne", then how could you be expected to write something as long as "for(i=0; i<a.length; i++)"? --Kainaw ^(talk) 16:35, 30 July 2006 (UTC)

Also, a comma, period, or semicolon would be a far better way to separate clauses than an ellipsis. And some additional advice on the debugging side: 1) A flow chart or some pseudocode can help you work out the logic more easily. 2) It doesn't matter how good your logic is if you use the wrong symbol or variable somewhere, so go through whatever you typed with a fine-toothed comb. I wonder, Kainaw, how much of a correlation there is between the two. I've never had the slightest problem with the complexities of logic and syntax in my programs, and I've also always had a thing for grammar and punctuation. Black Carrot 00:34, 31 July 2006 (UTC)

A quick calculation... I grade on average 52 programming assignments a year. There is an average of 40 students a class. So, I can safely say that I grade over 2,000 programming assignments a year. Because these are students, comments are required as 20% of the grade. I have found a strong correlation between grammar and programming. I'm not talking about words that are difficult to spell - such as correlation. I wouldn't think less of someone who used corelation or corellation. Then, there is teh in place of the. Very common one there when you are typing fast. However, a complete disregard for grammer usually results in a complete disregard for programming structure. --Kainaw ^(talk) 12:22, 31 July 2006 (UTC)

mIRC

I have several IRC-related questions. First, why is mIRC so popular? Second, I thought that mIRC was trial software with a 30 day trial period, so why is it that unregestered users are still using it years at a time? Third, I was wondering if anyone could recommend an IRC client to me for Windows, because I already went to the the IRC client comparison wiki and tried savIRC, but can't get it to use a SOCKSv5 proxy correctly. - Ridge Racer 17:30, 30 July 2006 (UTC)

I don't know about mIRC, but about another IRC client. Do you use Firefox? (If not, you should.) ChatZilla is a great IRC client for Firefox. —Mets501 (talk) 18:24, 30 July 2006 (UTC)

I do use Firefox and was thinking of using Chatzilla, although I was slightly more interested in a stand-alone client. (so many programs have irc clients bundled in these days and usually the quality is somewhat inferior) However, I suppose I can give it a shot. Any other sugestions are appreciated as well. - Ridge Racer 18:46, 30 July 2006 (UTC)

mIrc is used for many thinks not just chatin for downloading movies etc. u can still use mIrc even if the trail period is over u just click continue. i think irc is Ok it is not the best.

you can browse Category:IRC clients for Microsoft Windows and Category:IRC clients (which contains multiplatfrom clients). Jon513 21:12, 30 July 2006 (UTC)

Taking screenshots of DVDs

I'm trying to get a screenshot of a DVD I own. I'm familiar with the print screen option, pasting it into paint, and selecting the part I want and pasting it into another file. I've done it many times before. But every time I take a screenshot of the DVD, and after pasting it into paint and selecting what part I want, I paste it into a new file but all I get is the original image. Oddly (and this is really hard to explain, so bear with me) the original image is only partly shown, the rest is white background. My own cut out image still has the same size and dimensions, but instead I can drag it around and view the whole image. Also, I've noticed that when pasting the original image for the first time into Paint, there's a purple background on some parts of the image, and I can move the video screen (that is, the square that is playing the actual movie) around the canvas.

I'm really sorry that this is so complicated, but I've tried every player I have (InterActual, Windows Media, etc.). I'm using a Sony VAIO computer and playing the widescreen DVD, if that helps at all. Thanks.

That's because of the way software DVD players work. The windows GUI part just fills its display window with a special colour. They then set up somehardware registers, which map a chunk of the display adapter's memory as an "overlay" layer - the graphics hardware composits that overlay memory onto the screen just before it generates the final (usually analog) video output. So when you take a screen capture, all you capture is the "key" colour (our Chroma key programming makes a stab at explaining this). So you need a player that will generate the screencap itself. I think VideoLAN will do it. -- Finlay McWalter | Talk 23:14, 30 July 2006 (UTC)

Yes, I just verified VideoLAN's VLC media player does; you just pick "snapshot" from the context menu, and it saves a PNG in your "my pictures" folder. -- Finlay McWalter | Talk 23:18, 30 July 2006 (UTC)

Excellent, thanks a bunch. So, can I just download VideoLAN at their website for free?

Yes. It's free, open source, and fabtastic. It's multiregion, plays encrypted disks, lets you skip over those dull warnings and ads which the DVD maker marks as "non skipable", plays a huge range of other kinds of media, and (cleverest of all) you can set the client up to stream anything (even your playing DVD) over a network - so you can multicast the same DVD to every computer in your house or office. -- Finlay McWalter | Talk 00:03, 31 July 2006 (UTC)

Sorry for being an idiot, but you said to pick snapshot from the context menu. I downloaded the media player, but I can't find what you're talking about.

(I'm not 100% sure "context menu" is really the correct term anyway). Assuming you're playing a DVD (you did file -> open disk and picked DVD or DVD(menus) with the correct drive letter set. To take the screenshot, right-click on the playing movie, and pick "snapshot" from the menu that pops up. The screenshot is stored in your "My Pictures" folder - take multiple screenshots and they'll all pile up there. -- Finlay McWalter | Talk 00:10, 31 July 2006 (UTC)

Alright, problem solved. In my book, you're a freaking genius.

Another way to get around this is to temporarily disable hardware acceleration on your video card. It'll force the video card to pipe the DVD output through normally and you can use the regular "print screen" command. --Fastfission 05:13, 31 July 2006 (UTC)