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  • How do I generate a random string of up to a certain length?

    - by slavy13
    I would like to generate a random string (or a series of random strings, repetitions allowed) of length between 1 and n characters from some (finite) alphabet. Each string should be equally likely (in other words, the strings should be uniformly distributed). The uniformity requirement means that an algorithm like this doesn't work: alphabet = "abcdefghijklmnopqrstuvwxyz" len = rand(1, n) s = "" for(i = 0; i < len; ++i) s = s + alphabet[rand(0, 25)] (pseudo code, rand(a, b) returns a integer between a and b, inclusively, each integer equally likely) It doesn't work because shorter lengths are as likely as longer ones, meaning it's more likely to generate a shorter string than a longer one, so the result is not uniform.

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  • How do I generate a random time interval and add it to a mysql datetime using php?

    - by KeenLearner
    I have many rows in mysql table with datetime's in the format of: 2008-12-08 04:16:51 etc I'd like to generate a random time interval of anywhere between 30 seconds, and 3 days and add them to the time above. a) how do I generate a random time between 30 and 3 days? b) how do I add this time to the date time format above? I imagine i need to do a loop to pull out all the info, do the math in php, and then update the row... Any ideas?

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  • Why is using a Non-Random IV with CBC Mode a vulnerability?

    - by The Rook
    I understand the purpose of an IV. Specifically in CBC mode this insures that the first block of of 2 messages encrypted with the same key will never be identical. But why is it a vulnerability if the IV's are sequential? According to CWE-329 NON-Random IV's allow for the possibility of a dictionary attack. I know that in practice protocols like WEP make no effort to hide the IV. If the attacker has the IV and a cipher text message then this opens the door for a dictionary attack against the key. I don't see how a random iv changes this. (I know the attacks against wep are more complex than this.) What security advantage does a randomized iv have? Is this still a problem with an "Ideal Block Cipher"? (A perfectly secure block cipher with no possible weaknesses.)

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  • What could be causing Windows to randomnly reset the system time to a random time?

    - by Jonathan Dumaine
    My Windows 7 machine infuriates me. It cannot hold a date. At one point it all worked fine, but now it will decide that it needs to change the system time to a random time and date either in the future or past. There seems to be no correlation or set interval of when it happens. To remedy it I have: Correctly set the time in bios. Replaced the motherboard battery with a new CR2032 (even checked it with a multimeter). Tried disabling automatic internet synchronizing via "Date and Time" dialog. Stopped, restarted, left disabled the Windows Time service. Yet with all of these actions, the time will continue to change. Any ideas?

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  • Random BSODs on Win7 boot. Can't find a valid reason.

    - by 0plus1
    Hi, I bought and assembled a new pc: ASUS m4a785td-v EVO AMD x4 620 OCZ Black Edition 2x 2gb WD 500gb sata Win7 Ultimate 64bit fresh install BSOD on boot. Formatted, reinstalled, BSOD on install. Ran memtest - no errors. Ran Win7 install in safe mode. Installed, random BSOD on win7 startup, even in safe mode. Updated BIOS. Ran the win7 memtest (no error), booted after some tries and ran Prime95 blend test for 12 hours straight with no errors at all! When the pc has booted, win7 runs as smooth as possible, I've been playing STALKER for 4 hours straight with not a single hiccup. Using Blue Screen View I can see that every BSOD involves: ntoskrnl.exe Here are the dumps Any help would be greatly appreciated, this thing is driving me crazy.

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  • What could be causing Windows to randomly reset the system time to a random time?

    - by Jonathan Dumaine
    My Windows 7 machine infuriates me. It cannot hold a date. At one point it all worked fine, but now it will decide that it needs to change the system time to a random time and date, either in the future or past. There seems to be no correlation or set interval of when it happens. In attempt to remedy this, I have: Correctly set the time in BIOS. Replaced the motherboard battery with a new CR2032 (even checked it with a multimeter). Tried disabling automatic internet synchronizing via "Date and Time" dialog. Stopped, restarted, left disabled the Windows Time service. Yet with all of these actions, the time will continue to change. Any ideas?

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  • Apache crashing at random intervals. Can not find a reason in log files

    - by Nick Downton
    We are having an issue with a VPS running plesk 9.5 on ubuntu 8.04 At seemingly random intervals Apache will disappear and needs to be started manually. I have checked the apache error log, /var/log/messages, individual virtual host apache error files and cannot find anything that coincides with the time of the failure. dmesg is empty which is a bit odd. We have also had the psa service go down for no apparent reason but apache stay up. I'm at a loss to diagnose this really because all the log files I can find do not point to any issues. Are there any others I can look at? Memory usage sits at about 55% (out of 400mb) and it isn't a particularly high trafficed server. Any pointers as to where else I can find out what is going on would be very much appreciated. Nick

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  • is it okay to use random URLs instead of passwords?

    - by stew
    Is it considered "safe" to use URL constructed from random characters like this? http://example.com/EU3uc654/Photos I'd like to put some files/picture galleries on a webserver that are only to be accessed by a small group of users. My main concern is that the files should not get picked up by search-engines or curious power-users that poke around my site. I've set up an .htaccess file, just to notice that clicking on http://user:pass@url/ links doesn't work well with some browsers/email clients, prompting dialogs and warnings messages that confuse my not-too-computer-savy users.

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  • What are these completely random images that pop up when using Recuva?

    - by Qubert
    I just used Recuva to get back some photos I accidentally deleted on C:, but I also noticed there's a bunch of COMPLETELY random images in the list of recoverable files I can choose from. An example would be, There are images with names like John_Doe.jpg with a file path somewhere out of C:/Windows/Assembly/ And some of these things don't even make sense, there's one called componentsSpriteImage with the path C:/?/Images that shows a "poster" from the TV series Gold Rush. I am completely lost on this.. I know the OS is on C:, but I can't really think of a reason why Microsoft would leave a image hanging around from Gold Rush.

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  • Java - Draw Cards and Eliminate Cards Problem

    - by Jen
    I am having a problem in this question. I want a system inside a game wherein the player draws 2 cards randomly, and the enemy draws 2 cards randomly. Then, what the program does is to print out to the console the cards the player draw and the enemy's. The cards should not conflict and must not be the same. Then lastly, the program prints out the card that was not drawn by both the player and the enemy. Here's how I did it but it was lengthy and full of errors: import java.util.Random; public class Draw { public static Random random = new Random(); public static String cards[] = {"Hall", "Kitchen", "Billiard", "Study", "Pool"}; public static int playercounter; public static int enemycounter; public static String playercardA = null; public static String playercardB = null; public static String enemycardA = null; public static String enemycardB = null; public String lastcard = null; public static void playercardAdraw() { playercounter = random.nextInt(5); playercardA = cards[playercounter]; } public static void playercardBdraw() { playercounter=random.nextInt(5); playercardB= cards[playercounter]; if (playercardB==playercardA || playercardB == enemycardA || playercardB == enemycardB) { return; } } public static void enemycardAdraw () { enemycounter = random.nextInt(5); enemycardA=cards[enemycounter]; if (enemycardA == playercardA || enemycardA == playercardB) { return; } } public static void enemycardBdraw () { enemycounter = random.nextInt(5); enemycardB=cards[enemycounter]; if (enemycardB == playercardA || enemycardB == playercardB || enemycardB == enemycardA) { return; } } public static void main (String args []) { System.out.println("Starting to draw..."); System.out.println("Player's Turn: "); playercardAdraw(); System.out.println("Player's first card: " + playercardA); playercardBdraw(); System.out.println("Player's second card: " + playercardB); System.out.println("Enemy's Turn: "); enemycardAdraw(); System.out.println("Enemy's first card: " + enemycardA); enemycardBdraw(); System.out.println("Enemy's Second card: " + enemycardB); } }

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  • Draw Cards and Eliminate Cards Problem

    - by Jen
    I am having a problem in this question. I want a system inside a game wherein the player draws 2 cards randomly, and the enemy draws 2 cards randomly. Then, what the program does is to print out to the console the cards the player draw and the enemy's. The cards should not conflict and must not be the same. Then lastly, the program prints out the card that was not drawn by both the player and the enemy. Here's how I did it but it was lengthy and full of errors: import java.util.Random; public class Draw { public static Random random = new Random(); public static String cards[] = {"Hall", "Kitchen", "Billiard", "Study", "Pool"}; public static int playercounter; public static int enemycounter; public static String playercardA = null; public static String playercardB = null; public static String enemycardA = null; public static String enemycardB = null; public String lastcard = null; public static void playercardAdraw() { playercounter = random.nextInt(5); playercardA = cards[playercounter]; } public static void playercardBdraw() { playercounter=random.nextInt(5); playercardB= cards[playercounter]; if (playercardB==playercardA || playercardB == enemycardA || playercardB == enemycardB) { return; } } public static void enemycardAdraw () { enemycounter = random.nextInt(5); enemycardA=cards[enemycounter]; if (enemycardA == playercardA || enemycardA == playercardB) { return; } } public static void enemycardBdraw () { enemycounter = random.nextInt(5); enemycardB=cards[enemycounter]; if (enemycardB == playercardA || enemycardB == playercardB || enemycardB == enemycardA) { return; } } public static void main (String args []) { System.out.println("Starting to draw..."); System.out.println("Player's Turn: "); playercardAdraw(); System.out.println("Player's first card: " + playercardA); playercardBdraw(); System.out.println("Player's second card: " + playercardB); System.out.println("Enemy's Turn: "); enemycardAdraw(); System.out.println("Enemy's first card: " + enemycardA); enemycardBdraw(); System.out.println("Enemy's Second card: " + enemycardB); } }

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  • Slow Windows Explorer on Windows 7

    - by MadBoy
    I have Laptop with i7 (4 cores), 8GB ram and SSD OCZ Vertex 3 MaxIOPS which in testing that I did just now does 400mb/s+ read/write. However the responsiveness of Windows Explorer is far from being perfect. Opening up Computer, Documents, going into folders is very slow (1-5seconds). I don't have any viruses or spyware and I have tried changing properties to optimize view for General Items. I tried disabling Search Indexer but it made search in Outlook 2010 crawl and didn't bring any other effect. Even double clicking on file takes some time to open things up (like clicking a Word document). I don't have any drives mapped, my computer is not joined to domain. I have multiple VPN connections that I connect to but they all have disabled default gateways. I tried using CC Cleaner or some Windows 7 Tweaks app to disable some things. I am power user using Visual Studio, Tortoise SVN and other developer/administration apps. Any non obvious ideas? Edit: So I've been trying to pinpoint where the issue comes from and it seems that straight after reboot Windows Explorer opens very fast, when I load 3-4 programs (Royal TS, Visual Studio, Outlook) it's noticeably slower and the more programs I have it gets worse. After I start closing programs it starts working better and if I leave 2 open it's fast again. I tried doing some research with DiskMon and other programs from sysinternals but couldn't find anything suspicious. Below are stats during normal usage with a lots of programs open: - Ram usage with a lot of programs open and no swap file (i disabled it for testing): 6.95GB - CPU usage: 15%, none of the cores takes more then 50% (I have VS 2010 open x 4) HD Tune Pro: OCZ-VERTEX3 MI Benchmark Test capacity: full Read transfer rate Transfer Rate Minimum : 363.9 MB/s Transfer Rate Maximum : 505.5 MB/s Transfer Rate Average : Access Time : Burst Rate : CPU Usage : HD Tune Pro: OCZ-VERTEX3 MI File Benchmark Drive C: Transfer rate test File Size: 500 MB Sequential read 484102 KB/s Sequential write 444714 KB/s Random read 7779 IOPS Random write 16888 IOPS Random read (queue depth = 32) 73007 IOPS Random write (queue depth = 32) 69790 IOPS HD Tune Pro: OCZ-VERTEX3 MI Random Access Test capacity: full Read test Transfer size operations / sec avg. access time max. access time avg. speed 512 bytes 3260 IOPS 0.306 ms 2.106 ms 1.592 MB/s 4 KB 4161 IOPS 0.240 ms 2.006 ms 16.256 MB/s 64 KB 2382 IOPS 0.419 ms 2.367 ms 148.934 MB/s 1 MB 449 IOPS 2.225 ms 4.197 ms 449.407 MB/s Random 809 IOPS 1.235 ms 6.551 ms 410.527 MB/s HD Tune Pro: OCZ-VERTEX3 MI Extra Tests Test capacity: full Random seek 3975 IOPS 0.252 ms 1.941 MB/s Random seek 4 KB 4245 IOPS 0.236 ms 16.583 MB/s Butterfly seek 4086 IOPS 0.245 ms 1.995 MB/s Random seek / size 64 KB 3812 IOPS 0.262 ms 58.606 MB/s Random seek / size 8 MB 120 IOPS 8.348 ms 485.737 MB/s Sequential outer 4524 IOPS 0.221 ms 282.721 MB/s Sequential middle 4429 IOPS 0.226 ms 276.818 MB/s Sequential inner 5504 IOPS 0.182 ms 344.000 MB/s Burst rate 4472 IOPS 0.224 ms 279.475 MB/s

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  • COM+/Desktop Heap errors in IIS affecting sites at random?

    - by tresstylez
    We have a Win2K3 server that is hosting 30+ sites. Each site is configured to have its own unique application pool -- so that we can manually recycle specific sites if needed and not kill sessions for the others. From what I've read, the consequence of this type of setup is that each application pool worker process gets allocated a Desktop Heap (normally 512 kb's) and we limit the number of app pools we can serve. http://blogs.msdn.com/b/david.wang/archive/2006/01/25/security-considerations-of-usesharedwpdesktop-on-iis6.aspx PROBLEM: What we're seeing is that occasionally COM+ errors get triggered, presumably by hitting our 512 kb limit of the desktop heap -- and certain sites become unresponsive (or have errors) until we manually recycle that specific app pool. I know that I can increase the desktop heap limit to 1024, and make other tweaks/tunes, but I've been tasked with finding out what exactly causes one site's heap to max out as opposed to another. It seems that when we start seeing COM+ errors, the sites it affects are random -- small sites or big sites (heavier used). Is it based on process id? Traffic? Any pointers on understanding this a little more would be excellent. Thanks! jg

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  • This program runs but not correctly; the numbers aren't right.

    - by user320950
    this program runs but not correctly numbers arent right, i read numbers from a file and then when i am using them in the program they are not right.:brief decription of what i am trying to do can someone tell me if something doesnt look right. this is what i have to do: write a program that determines the grade dispersal for 100 students You are to read the exam scores into three arrays, one array for each exam. You must then calculate how many students scored A’s (90 or above), B’s (80 or above), C’s (70 or above), D’s (60 or above), and F’s (less than 60). Do this for each exam and write the distribution to the screen. // basic file operations #include <iostream> #include <fstream> using namespace std; int read_file_in_array(double exam[100][3]); double calculate_total(double exam1[], double exam2[], double exam3[]); // function that calcualates grades to see how many 90,80,70,60 //void display_totals(); double exam[100][3]; int main() { double go,go2,go3; double exam[100][3],exam1[100],exam2[100],exam3[100]; go=read_file_in_array(exam); go2=calculate_total(exam1,exam2,exam3); //go3=display_totals(); cout << go,go2,go3; return 0; } /* int display_totals() { int grade_total; grade_total=calculate_total(exam1,exam2,exam3); return 0; } */ double calculate_total(double exam1[],double exam2[],double exam3[]) { int calc_tot,above90=0, above80=0, above70=0, above60=0,i,j, fail=0; double exam[100][3]; calc_tot=read_file_in_array(exam); for(i=0;i<100;i++) { for (j=0; j<3; j++) { exam1[i]=exam[100][0]; exam2[i]=exam[100][1]; exam3[i]=exam[100][2]; if(exam[i][j] <=90 && exam[i][j] >=100) { above90++; { if(exam[i][j] <=80 && exam[i][j] >=89) { above80++; { if(exam[i][j] <=70 && exam[i][j] >=79) { above70++; { if(exam[i][j] <=60 && exam[i][j] >=69) { above60++; { if(exam[i][j] >=59) { fail++; } } } } } } } } } } } return 0; } int read_file_in_array(double exam[100][3]) { ifstream infile; int exam1[100]; int exam2[100]; int exam3[100]; infile.open("grades.txt");// file containing numbers in 3 columns if(infile.fail()) // checks to see if file opended { cout << "error" << endl; } int num, i=0,j=0; while(!infile.eof()) // reads file to end of line { for(i=0;i<100;i++) // array numbers less than 100 { for(j=0;j<3;j++) // while reading get 1st array or element infile >> exam[i][j]; infile >> exam[i][j]; infile >> exam[i][j]; cout << exam[i][j] << endl; { if (! (infile >> exam[i][j]) ) cout << exam[i][j] << endl; } exam[i][j]=exam1[i]; exam[i][j]=exam2[i]; exam[i][j]=exam3[i]; } infile.close(); } return 0; }

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  • What could cause random files being downloaded without permission?

    - by Dustin
    I have been having issues lately with a certain directory. It seems someone is placing files into it, or something of that sort, and any attempt to delete them is successful, HOWEVER they reappear over time (maybe not the exact same ones, but random files). I will provide you the information I can and several pictures of my problem: sandbox.mys4l.com/visual/files/b1.jpg Files like this have been appearing in my /visual/ folder, and I have no clue where they are coming from. sandbox.mys4l.com/visual/files/b2.jpg This is what is inside on of those weird files, it appears to be nothing problematic. sandbox.mys4l.com/visual/files/b4.jpg As you can see, in the time it took me to take the first picture, more odd files showed up. These log files are also being uploaded to this directory, and I know I didn't put them there. sandbox.mys4l.com/visual/files/b7.jpg This inside one of these mysterious .log files, I'm not sure what it's all about. These files only appear to be going into this specific area, and I'm not sure of their origin, only that they will not go away. I have done a full system scan at least twice with an up-to-date virus scan, and have looked for an unknown script which may be writing them there. Nothing has come up, so I come to you guys as I hear this is the best place to find answers. Hope this problem has a solution!

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  • Computer always freezing after random periods of time. No errors listed.

    - by Wesley
    Hi, all. Here are my specs beforehand: AMD Athlon XP 2400+ @ 2.00 GHz, 160GB IDE HDD, 128MB GeForce 6200 AGP, 2 x 512MB PC3200 DDR RAM, CoolMax 350W PSU, 1 x CD-RW Drive, 1 x DVD-ROM Drive, FIC AM37 Mobo, Windows XP Pro SP3 My desktop freezes after random periods of time but there are no errors listed in the Event Viewer after a forced shutdown and restart. A couple months ago, I found that when it froze, the floppy was being accessed at the same time. So, I disconnected the floppy (since I never used it anyways) from the power supply and motherboard. Everything was working fine and the computer never froze. This past Christmas break, I left for a Conference and when I got home, the computer kept freezing again. So, this time, I just disconnected the DVD reader (from mobo and power) and started it up. Still, it froze almost right away. Then I found some older sticks of RAM (2 x 256MB PC2100 DDR) and swapped them in. Everything worked fine again after that. I even swapped the 2 x 512MB PC3200 DDR RAM back in and everything worked okay. Then it started freezing again, and I tried all possible RAM combos, still freezing within 5-10 minutes of startup. One thing I've realized is that the floppy drive is still listed in My Computer and I uninstalled it from my Device Manager already. There were no software errors, and I uninstalled the most recent software, with no effect. Still, I have no idea what is wrong because everything ran fine before that. Any suggestions? EDIT: Still have yet to buy some blank CD media to use Memtest86+. However, would a lack of virtual memory cause the computer to freeze? EDIT2: So after a long time, I ran Memtest86+ and all is well. Turns out though, after removing my original DVD reader and replacing it with a DVD-ROM drive, there is no freezing whatsoever! Thanks for all your suggestions!

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  • What could cause random files being uploaded without permission?

    - by Dustin
    I have been having issues lately with a certain directory. It seems someone is placing files into it, or something of that sort, and any attempt to delete them is successful, HOWEVER they reappear over time (maybe not the exact same ones, but random files). I will provide you the information I can and several pictures of my problem: sandbox.mys4l.com/visual/files/b1.jpg Files like this have been appearing in my /visual/ folder, and I have no clue where they are coming from. sandbox.mys4l.com/visual/files/b2.jpg This is what is inside on of those weird files, it appears to be nothing problematic. sandbox.mys4l.com/visual/files/b4.jpg As you can see, in the time it took me to take the first picture, more odd files showed up. These log files are also being uploaded to this directory, and I know I didn't put them there. sandbox.mys4l.com/visual/files/b7.jpg This inside one of these mysterious .log files, I'm not sure what it's all about. These files only appear to be going into this specific area, and I'm not sure of their origin, only that they will not go away. I have done a full system scan at least twice with an up-to-date virus scan, and have looked for an unknown script which may be writing them there. Nothing has come up, so I come to you guys as I hear this is the best place to find answers. Hope this problem has a solution!

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  • Python: How can I read in the characters from a line in a file and convert them to floats and strs, depending on if they are numbers or letters?

    - by user1467577
    I have a file that looks like: 1 1 C C 1.9873 2.347 3.88776 1 2 C Si 4.887 9.009 1.21 I would like to read in the contents of the file, line-by-line. When I only had numbers on the lines I used: for line in readlines(file): data = map(float, line.split) But this only works when all the elements of line.split are numbers. How can I make it store the letters as strings and the numbers as floats?

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