Wikipedia:Reference desk/Archives/Computing/2011 February 15

= February 15 =

Maximum Length of Petaflop-Year Crackable AES-128 Password
What is the maximum possible length of a AES-128 password used to encrypt text of length 1024 bytes, which can be brute-force decrypted with one petaflop of computing power in one year? In other words, how short does an AES-128 password have to be to be cracked with one petaflop of computing power in one year? This is not a homework question. Rocketshiporion ♫ 00:18, 15 February 2011 (UTC)


 * As I said before, AES doesn't define any way of encrypting a file with a password. Everyone has a different way of doing it. Supposing that your chosen encryption format's key derivation function takes a typical modern computer 0.1 second to compute, and your petaflop cluster is, I dunno, 100,000 times faster than that, then it can test 1,000,000 passwords per second, or 245 per year. So the answer is a password with about 45 bits of entropy. This page will give you examples of random-character passwords with varying amounts of entropy. Note that the answer is independent of whether you're using AES-128, AES-256, Salsa20, or what-have-you to actually encrypt the plaintext. It depends only on the key derivation time, which varies over many orders of magnitude in real-world encryption software. -- BenRG (talk) 10:39, 15 February 2011 (UTC)


 * Just to clarify, by 45 bits of entropy, do you mean a password with 45 random characters? Rocketshiporion ♫ 23:18, 15 February 2011 (UTC)


 * No, shorter than that. It means, more or less, that you picked the password at random from a set of 245 possible passwords. For example, a password of 10 random uppercase letters would have about 47 bits of entropy because 2610 ≈ 247. The page I linked calls it "strength" instead of "entropy", and it could also be called "randomness". It's not really a well defined concept because it's often not clear what the set is that you're selecting from or what it means to select uniformly from that set, but it's the best answer that can be given to your original question. -- BenRG (talk) 07:02, 16 February 2011 (UTC)


 * Ah! That answers my question perfectly. Thank you! Rocketshiporion ♫ 05:06, 18 February 2011 (UTC)

Replacing a processor
Hiya WP! I'm planning to replace my belowed computer's processor in the near future. The current one is an adequate Celeron. What should I bear in mind when choosing a new one? 212.68.15.66 (talk) 10:28, 15 February 2011 (UTC)
 * Make sure your motherboard model supports the new processor. If it's a celeron, it may be somewhat difficult to come by a processor that will work with the motherboard.  In my experience, after a few years replacing the processor means replacing the Motherboard, CPU, and RAM at the same time.  You might get lucky though and the motherboard could support a Core 2 Duo! 206.131.39.6 (talk) 17:36, 15 February 2011 (UTC)


 * This could be the start of an eternal upgrade similar to what I do. I first upgraded my motherboard to the best motherboard that supported all my old hardware. Then, the next year, I upgraded by processor. The next year, I upgraded my RAM. The next year, I upgraded my CD player to a CD burner. The next year, I upgraded my video card to a fancy dual-head card. The next year, I replaced my CRT with two LCD monitors. The next year (due to power issues) I upgraded my 250W power supply to a 500W power supply. Then, I upgraded the motherboard again and started a whole new cycle. Last year, I upgraded my old IDE harddrive with two SATAs that mirror each other. I figure I'll keep upgrading one thing every year instead of purchasing a new computer. -- k a i n a w &trade; 17:47, 15 February 2011 (UTC)


 * CPU speed improvements in the past few years have not been spectacular. Fortunately, for most applications, CPU speeds are already so incredibly fast as to be irrelevant.  There are a few cases where CPU speed matters (scientific simulations, raytracing, databases), but most computing is RAM-limited.  If the computer is paging at all, it'll probably benefit more from a modest RAM upgrade than any amount of CPU.  Even if it isn't paging, it's worthwhile to have extra RAM to use as hard drive cache.  As a bonus, RAM is usually easier to upgrade than a CPU.  Paul (Stansifer) 18:15, 15 February 2011 (UTC)


 * If you're upgrading your computer, RAM is your best friend. I have 144GB of regular RAM in my computer, and everything runs incredibly fast because my computer doesn't use a pagefile. If you have to use a pagefile, either put the pagefile on a PCIe SSD or (if you're cost-concious) use a SATA III SSD as your boot drive, and put the page file on that. If your motherboard supports Core 2 processors, consider getting a Core 2 Quad instead of a Core 2 Duo. The extra threads permit more applications to simultaneously run faster on your computer. Rocketshiporion ♫ 00:01, 16 February 2011 (UTC)

Vector in C++ and maths
In C++, a vector is a one-dimensional array. I was wondering about the origin of the name, as it seems to have nothing to do with the vectors in mathematics. Anyone know? 212.68.15.66 (talk) 11:10, 15 February 2011 (UTC)
 * A mathematical vector is often represented as a column of numbers (similar to a matrix with a single column). This seems close to the idea of a one-dimensional array in computer science.  Certainly, a C++ vector can be used to represent a mathematical vector (a direction vector of dimensionality N can be represented by a vector of length N), and the term vector processor seems to reference both meanings (it can be used for adding mathematical vectors, and acts on CS vectors).  However vector does have many meanings in both math and computer science. --Colapeninsula (talk) 11:43, 15 February 2011 (UTC)
 * You, sir, are awesome. Thanks! 212.68.15.66 (talk) 12:02, 15 February 2011 (UTC)
 * See also row vector and column vector. --Sean 16:39, 15 February 2011 (UTC)

Slow ADO Query over Access with VB6 over a LAN
My program uses MS Access as DB and Visual Basic 6. I've experienced an issue loading a recordset with about 300000 records, some fields indexed, when I place a SELECT SELECT * from Materials m INNER JOIN Quantity s ON m.code=s.materialcode ORDER BY code

in a ADO recordset with the following configurations:

Provider: Jet;OLEDB CursorType: adOpenForwardOnly LockType: adLockReadOnly CursorLocation: adUseClient


 * I place the query and pass to a datagrid, I've not to edit or modify the records ***

Strangely, if I use on the same machine where I've the .mdb file is fast, from other clients is slow (approx. 15 seconds).

What Can I change? Thanks. — Preceding unsigned comment added by Frankge973 (talk • contribs) 13:28, 15 February 2011 (UTC)

sound from heal
Can radar and wi-fi or hand-phone line or sate lit can receipt Frequencies from health and send it to every human ear?Example:me want to say halo to some person... me not use mouth to talk just use energy inside body and make some frequencies come out from the heal than use hardware radar and wi-fi or hand phone line or sate lit detect that frequencies come out inside body than lead into computer and use software filter the frequency than use computer send and connect to the radio station and sate lit lead the frequency into some person ears than the person will no need any electronics and this person also can receipt my sound halo from sate lit frequency..... — Preceding unsigned comment added by Jackfengyi (talk • contribs) 16:11, 15 February 2011 (UTC)


 * See Stephen Hawking. He uses a slight wiggle to send a signal to a device which converts it to input to a computer which manages the signals to put together text which is then converted into sound waves which are converted into electric signals that are sent to speakers which vibrate air which allows others to hear him say "Hello." -- k a i n a w &trade; 17:43, 15 February 2011 (UTC)


 * You might also be interested in subvocal recognition, though I don't think any of that technology has made it beyond the lab yet. the wub "?!"  18:53, 15 February 2011 (UTC)


 * The OP's use of English makes it very difficult for me to understand the question. However, I think he is asking if some kind of electronically augmented telepathy would be possible.  If so, he might find the work of Kevin Warwick interesting.  Dr. Warwick's work has involved the implantation of electrodes in his brain.  The electrodes were connected to the internet and allowed him to control a robotic hand from thousands of km away - if I remember correctly, the documentary I saw a couple of years ago featured this experiment where the robotic hand was in a lab somewhere in the USA, while Dr. Warwick controlled it from his office in the UK.  Astronaut (talk) 23:42, 15 February 2011 (UTC)

NEW MOTHERBOARD
I want to buy a new motherboard. I have a 3.2 Intel processor and wanted to know if it'll be compatible with the new motherboard. It's an; Intel - Classic Series "Trinity Valley" G41 Motherboard. The features of the motherboard are:
 * 1) The Intel Desktop Board DG41TY with microATX form factor offers legacy to premium features.
 * 2) Parallel port, integrated VGA & DVI ports, Intel HD Video experience, Intel High Definition Audio and integrated 10/100/1000 network connection, enrich your multimedia creation experience.
 * 3) The Intel Desktop Board DG41TY supports Intel Core2 Quad processors and Intel Core2 Duo processors and is Microsoft Windows Vista Premium WHQL certified.


 * 1) Intel - Classic Series ""Trinity Valley"" G41


 * 1) Socket LGA775 @ FSB1333 - For Celeron, Pentium Series & Core 2 Series CPU's
 * 2) 2x DDR2-800 (Dual)
 * 3) 4x SATAII, 1x ATA100.
 * 4) 1x PCI Express x16
 * 5) 1x PCI Express x1
 * 6) 2x PCI Slots
 * 7) 8x USB 2.0 (6x Cable)
 * 8) Intel GMA X4500 VGA
 * 9) Integrated Intel 6ch HD Audio Codec
 * 10) Integrated Gigabit LAN
 * 11) MicroATX  —Preceding unsigned comment added by 41.215.117.157 (talk) 19:50, 15 February 2011 (UTC)


 * The two things that really matter are the socket on the motherboard and the type of processor you have. Unfortunately "3.2" (presumably meaning 3.2 GHz) doesn't identify the processor, so the question can't be answered at this point. Looie496 (talk) 20:50, 15 February 2011 (UTC)

Welcome to the Wikipedia RefDesk. Please try not to type in ALL CAPS. It's the online equivalent of screaming. Thanks. Rocketshiporion ♫ 00:05, 16 February 2011 (UTC)

Get silverlight
I have updated Silverlight but the get silverlight website still says that I have an old version! I have checked with the silverlight about and the add/remove and it says that I have 4.06, the latest version! See http://img717.imageshack.us/f/silverlight.png/ --Tyw7 (☎ Contact me! • Contributions)   Changing the world one edit at a time! 20:41, 15 February 2011 (UTC)


 * Have you closed all browsers and restarted? Have you tried rebooting?  Nimur (talk) 23:24, 15 February 2011 (UTC)
 * I even tried down right reinstalling. Uninstall, reboot and visit site Sliverlight not detectected. Installed silverlight reboot, old version detected. When I visit another site to check silverlight version, that site shows the correct silverlight version I have installed. When I tried to run the downloader and install it it says same version detected. Can you try it on your pc with ie8 and post me the screenshot. Emailed Microsoft, waiting for response --Tyw7 (☎ Contact me! • Contributions)   Changing the world one edit at a time! 01:14, 16 February 2011 (UTC)

When pdf files fail
I have opened a pdf file with Acrobat Reader and Document Viewer, both in Ubuntu. The Acrobat view looks 'strange' and I'm sure that it was not what the author intended, with its cluttered font. The Document Viewer view, on the other side, has a normal font, which looks like Times New Roman. I thought that pdf files looked always right (that was the idea, I thought), but somehow this one do not has the fonts at hand. How can I discover which fonts are missing and solve this problem? Quest09 (talk) 20:43, 15 February 2011 (UTC)


 * evince (which is probably what you mean by Document Viewer) has a "properties" option in its File menu, which has a fonts tab. This lists fully and partially embedded fonts, and should list fonts that it gets from the system. Okular has the same thing.   Searching around suggests the same feature is available in Adobe Reader at "File -> Document Properties -> Fonts".  I don't have a PDF with non-embedded fonts to see exactly how it behaves in that case. -- Finlay McWalter ☻ Talk 21:48, 15 February 2011 (UTC)


 * Yes, I meant evince. And, yes, the problem seems that the author didn't embedded the fonts into the doc. I suppose, however, that both tried to guess a font, but evince had a better pick. Quest09 (talk) 22:49, 15 February 2011 (UTC)


 * I'd be interested to see a PDF with such an external font reference. If it's publicly available, could you link to it? -- Finlay McWalter ☻ Talk 22:52, 15 February 2011 (UTC)


 * Sure. Take a look at: <1 MB. Quest09 (talk) 01:30, 16 February 2011 (UTC)


 * Yes, you're right. The fonts it needs are in the Microsoft Core Fonts distribution, so you might try installing that. -- Finlay McWalter ☻ Talk 11:20, 16 February 2011 (UTC)
 * I tried viewing the PDF with Foxit and it looks OK :/ You might want to try foxit as it is smaller and lighter --Tyw7 (☎ Contact me! • Contributions)   Changing the world one edit at a time! 15:33, 16 February 2011 (UTC)


 * The problem here is not the viewer in question, it is the font available in Windows that is not available in Linux. Quest09 (talk) 17:47, 16 February 2011 (UTC)


 * No such font. ¦ Reisio (talk) 13:47, 17 February 2011 (UTC)
 * I don't know how it happened, but I just opened the document (Evince, Fedora 13, standard fonts, never added anything) and it looks just fine (see here, I included the fonts dialogue box from Evince for you). The font picked by the application seems to be Liberation Sans (~Arial). Normally the application should try to replace any font it doesn't know with anything it has at its disposal locally. --Ouro (blah blah) 10:50, 18 February 2011 (UTC)