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    Security Override Hacking Challenges Programming Challenges
    Programming 13
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    10-17-2010 08:54 PM Programming 13 | Edited by l0nwlf 10-18-2010 02:44 AM
    Regarding programming 13, I had done all the preprocessing stuff but am not clear on what the question wants,
    I converted the barcode image into a string with Black strip as 1, White strip as 0 and Turquoise strip as X, we get the string in the format as mentioned below.
    '10101101110111011010001101110110110001011011101011110111011011110101111010111011XXXXXXX101'
    Since barcode starts and end with '101' we remove that and removinn the X at the end gives us the string
    '01101110111011010001101110110110001011011101011110111011011110101111010111011'
    Converting it to ASCII we get, '7;#;17/;==;'
    According to wiki page of Code39 ( http://en.wikipedia.org/wiki/Code_39 ), I decode it for 'H%F/C%F17/O%F%H%H%F'
    Now what ? The question says the example as 123:7, but it doesnt make much sense. Any clues as to what the question want, am ready with all processing, just to understand the question and compute the solution.
     
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    10-17-2010 09:10 PM RE: Programming 13
    Yeah I agree the example is immensely confusing as to what the challenge requires. My best guess is it wanted the number of lines and the position of the turquoise one but that doesnt really make much sense either.
     
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    10-17-2010 09:27 PM RE: Programming 13
    You're going to have to learn about barcodes for this one.

    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc.htm
    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc1.htm
    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc2.htm
    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc3.htm

    securityoverride.net/images/userbar.png
     
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    10-17-2010 11:48 PM RE: Programming 13 | Edited by madf0x 10-17-2010 11:49 PM
    I know about bar codes, I read extensively about them when I had a sort of SQL injection idea about barcodes(petered out cause the barcodes got too long). The question is what the the challenge asking for, not how is it done. How do you achieve a result if you don't even know what type of result youre looking for? Youre better off just bruteforcing random numbers into the field and figure out what it wanted from the reward screen(maybe).
     
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    10-18-2010 12:49 AM RE: Programming 13
    It wants you to scan the barcode and return the value it needs. the left of the turquois would be some number and then you write a : and then the check digit.At least that what it seems to me.
     
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    10-18-2010 04:41 PM RE: Programming 13
    Null Set wrote:
    It wants you to scan the barcode and return the value it needs. the left of the turquois would be some number and then you write a : and then the check digit.At least that what it seems to me.

    Yes, that is correct.

    Decode the barcode up until the turquoise strip.
    Add each up.

    Find the check digit.

    Submit as sum:check

    securityoverride.net/images/userbar.png
     
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    10-18-2010 05:59 PM RE: Programming 13 | Edited by OnlyHuman 10-18-2010 06:48 PM
    Oops! Disregard my previous post. Reading failure on my part. Sad
    Back to work on my solution.
     
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    10-18-2010 06:55 PM RE: Programming 13
    I gotta admit, this don't make sense Sad reading this just makes it worse:

    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc3.htms/upc3.htm


    The three is 1-4-1-1 (space-bar-space-bar).


    How the f**k is 1-4-1-1 a three? and 3-2-1-1 three zeros??

    Confused!!!
     
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    10-18-2010 06:56 PM RE: Programming 13
    blandyuk wrote:
    I gotta admit, this don't make sense Sad reading this just makes it worse:

    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc3.htms/upc3.htm


    The three is 1-4-1-1 (space-bar-space-bar).


    How the f**k is 1-4-1-1 a three? and 3-2-1-1 three zeros??

    Confused!!!

    It's the pattern. The pattern of 1-4-1-1 (alternating between black and while) is equivalent to a 3.

    securityoverride.net/images/userbar.png
     
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    10-18-2010 10:57 PM RE: Programming 13
    I think I have cracked it, still it is giving me wrong answer.
    Let's say for a barcode I decoded the area before the turquoise strip as '28653732279', now I assume by sum you does not mean sum of individual digit i.e. 54. Now calculating the checkdigit the solution will be 28653732279:6, If I am assuming the method to calculate the checkdigit as correct. The biggest issue in this question is "How to verify ?".
    The image without logging in to securityoverride gives - http://securityoverride.com/challenges/programming/13/img.php , the solution being '00000000000:10'. I suggest you change that to any sample data and give us the solution or give us a sample barcode with correct answer. The problem itself is not really tough but a slight amount of ambiguity makes it so.
     
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    10-18-2010 11:51 PM RE: Programming 13
    l0nwlf wrote:
    I think I have cracked it, still it is giving me wrong answer.
    Let's say for a barcode I decoded the area before the turquoise strip as '28653732279', now I assume by sum you does not mean sum of individual digit i.e. 54. Now calculating the checkdigit the solution will be 28653732279:6, If I am assuming the method to calculate the checkdigit as correct. The biggest issue in this question is "How to verify ?".
    The image without logging in to securityoverride gives - http://securityoverride.com/challenges/programming/13/img.php , the solution being '00000000000:10'. I suggest you change that to any sample data and give us the solution or give us a sample barcode with correct answer. The problem itself is not really tough but a slight amount of ambiguity makes it so.

    http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/upc.htm

    securityoverride.net/images/userbar.png
     
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    10-19-2010 12:27 AM RE: Programming 13
    @anyone who was having trouble with the challenge before, view the updated news post. You may or may not have been confused by the lack of the 1-1-1-1-1 pattern in the middle of the barcode, but regardless, it is now present.

    securityoverride.net/images/userbar.png
     
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    10-19-2010 02:19 AM RE: Programming 13 | Edited by OnlyHuman 10-19-2010 02:21 AM
    I think there's a problem with the update. I tried rewriting my code to reflect the change. It should have been a simple fix, given the nature of my solver, but no matter what I did, I couldn't get it right. So, I worked it out by hand, and the pattern for the sixth and eleventh digits are corrupt within the image. Here's an example of one I decoded by hand.

    Download source  Code
    101 [3-1-1-2] [1-1-1-4] [3-2-1-1] [1-2-1-3] [1-2-1-3] [ 1-2-3 ] 01010 [1-1-1-4] [2-2-2-1] [1-1-3-2] [1-2-1-3] [1-4-1] CHECK 101




    Notice that the 6th and 11th patterns are both missing the final digit. It's fairly simple to guess them based on the available patterns. But I don't think this is what you intended, so I thought I'd bring it to your attention.
     
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    10-19-2010 03:56 AM RE: Programming 13 | Edited by l0nwlf 10-19-2010 03:57 AM
    Here is what I came up with.
    The barcode after Image processing breaks in the form :
    '101000101100110010011001011101101000110110000B0B01000010100100010010001110010110011XXXXXXX101'
    1 = Bars, 0 = Spaces, B = Blue bar, X = Turquoise bar.
    The string starts and end with '101', which is correct. And in the middle there is Space-Blue Bar-Space-Blue bar- Space.
    Removing starting and ending '101' and splitting it in two parts we get,
    part1 = '00010110011001001100101110110100011011000'
    part2 = '1000010100100010010001110010110011XXXXXXX'
    The length of both are 41 respectively, however they should have been of leghth 42. (6 X 7) i.e. 1 bit is missing from both columns.
    The image size should be 95X65 and not 93X65, after adding a 5 bar seperator. As OnlyHuman pointed out, there do exist one single bit error on both parts.
     
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    10-19-2010 04:42 AM RE: Programming 13
    Ah Smile many thanks to OnlyHuman, got it basically working but there is defo a problem with the barcode image. All codes work until I got to the 6th part, then I've not been able to match a number, even with the end part of it missing. Maybe I can run it a few times and one will work, not ideal but...
     
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    10-19-2010 04:57 AM RE: Programming 13
    Regarding the missing part, you can always check by adding a bar or a space, and then check whether a decoding for them exist. Kinda works for me, although I am still getting 'string not matched'. Sad
    Am pretty sure my check digit part is correct too, 10 - { (odd*3 + even) mod 10 } , Don't really understand where the fault is.
    @Qwexotic: Can we get sample data ? A barcode with its correct solution.
     
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    10-20-2010 04:48 PM RE: Programming 13
    Ok, programming 13 should really be fixed now. When I last "fixed" the challenge, two of the lines were offset by 1 pixel, which threw the whole image off by 2 pixels. But it has been fixed, and I have checked an image for verification. However, if anyone is still not getting this challenge to work, I might post an example image and solution.

    securityoverride.net/images/userbar.png
     
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    10-20-2010 04:52 PM RE: Programming 13 | Edited by OnlyHuman 10-20-2010 04:54 PM
    You got it! Whatever you did, works.
     
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    10-20-2010 09:07 PM RE: Programming 13
    I just redid my solution and it works. Smile
    However there is a little flaw ( which I'm sure will not hamper anyone to get correct solution ). The turquoise bars are only six in numbers now. Shouldn't they be seven i.e. the correct image size should be 95X65 and not 94X65.
     
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    10-20-2010 09:17 PM RE: Programming 13
    l0nwlf wrote:
    I just redid my solution and it works. Smile
    However there is a little flaw ( which I'm sure will not hamper anyone to get correct solution ). The turquoise bars are only six in numbers now. Shouldn't they be seven i.e. the correct image size should be 95X65 and not 94X65.

    Oh, my bad, fixing now. Smile

    securityoverride.net/images/userbar.png
     
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