Hash Function For 2D Barcode Data?
Mar 16, 2011
I am writing a string of about 120 characters to a 2D barcode. Along with other text, the string contains a unique ticket number. I want to ensure that someone doesn't generate counterfeit tickets by reading the 2D barcode and generation their own barcoded tickets.
I would like to hash the string and append the hash value to what gets embedded in the barcode. That way I can compare the two on reading and see if the data had been tampered with. I have seen several hash function that return 64 bytes and up but the more characters you embed in a 2D barcode the bigger the barcode image becomes. I would like an algorithm that returns a fairly small value. It would also be nice if I could provide the function my own key. Collision is not that big of a deal. This isn't any kind of national security application.
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Apr 20, 2012
I am trying to convert Bob Jenkins perfect hash function from C# to VB.Net and I am stuck at following.
a += (UInt32)(url[k + 0] + (url[k + 1] << 8) + (url[k + 2] << 16) + (url[k + 3] << 24))
How can I write above statement in VB.Net?
a is UInt32
url is String
k is Integer
I tried the following but it doesn't work.
a += url(k + 0) + (url(k + 1) << 8) + (url(k + 2) << 16) + (url(k + 3) << 24)
To avoid manually doing type casting, I am using "Option Strict Off"
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Sep 17, 2009
Does anyone have a working class or function to create the hashed email that is sent to facebook to register email addresses with connect.registerUsers?
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Apr 18, 2012
I need to hash a number (about 22 digits) and the result length must be less than 12 characters. It can be a number or a mix of characters, and must be unique. (The number entered will be unique too). For example, if the number entered is 000000000000000000001, the result should be something like 2s5As5A62s. I looked at the typical, like MD5, SHA-1, etc., but they give high length results.
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Aug 2, 2010
I am using Richard L. Grier's Enhanced Serial Port dll to read input from a serial port barcode scanner I notice that the datareceived event fires only once per barcode scan, but the delegate sub fires twice per barcode scan. Once for 1st half of Barcode , 2nd for 2nd part of barcode This makes it hard to capture the full barcode so it can be passed to routines in my vb.net 2008 windows application In Richard's example 'Test Enhanced Port' program he sends it to a textbox using .selectedtext and it works fine Richards Delegate code ......................
Public Delegate Sub DisplayData(ByVal Buffer As String)
'This delegate routine marshals receive data from the receive thread context DataReceived to the Windows Form STAThread context
Private Shared Sub Display(ByVal Buffer As String)
[code]....
I am trying to set a variable to the full barcode to pass to routines, instead of writing to a textbox but am not having any success
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Mar 19, 2009
Currently I add data to a hash table, then later on I loop through the hash table. To my horror I discovered that when you use FOR EACH with a hash table it doesn't return the items in the order you added them.I'm looking for a collection that I can add, edit and delete items from and loop through from start to end in that order.
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Nov 27, 2009
I am a student and I am about to make a program that will use a barcode scanner well ofcourse to scan a barcode. My problem is i don't know what library to use and what certain things i need to do so that when i am going to scan a barcode it'll be something like show it on a textbox and pull something from the database. i've actually research some. i've seen mscomm1 (not so sure about that) and POS for .net (haven't fully understood its use) were those will help me develop my program?i have a metrologic ms9520 Voyager barcode scanner. and i am going to create a program for it in vb2005.
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Jan 31, 2011
I tried to follow this advice, but I still run out of memory.
[URL]
Basically, I am reading all the bytes of a 1 gb disk and I want to try and do a md5 hash on it. However, when following this example, my cryptostream gets too large a System out of memory exception.
Is there another way to do the md5 hash over some much data?
I am currently reading it into 10 million bytes arrays at a time. Can I hash the first array, and then use it as a seed for the next array, and so one, like you might do to a CRC32 calculation?
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May 25, 2012
I have a case where I need to create barcodes to a Crystal Reports 2008 report (but this isn't as much about Crystal Reports in the end). But after a day's worth of googling I've become quite puzzled with all the different methods of encoding barcode data and all the various fonts.
I downloaded a free Code128 font from [URL] and also a program that can encode text into suitable format for the barcode font to use from here [URL] Now that works splendidly with the font installed, but the problem is that Crystal Reports does not recognize it as a barcode font when printing. It shows up fine in designer and when printing it out to PDF, but in my application's CrystalViewer it is shown as Arial font and the same goes for printing. Yet it can be succesfully exported as a PDF file via Crystal, and the barcode shows up fine. This is all on the same computer so the font is installed properly obviously.
So anyways, I noticed that Windows 7 comes with its own Code128, Code128A, B and C fonts. THEY show up properly (but are not readable because I don't know the proper control characters) in every place I need them to, but I can't for the life of me understand how to encode suitable data for them. The previously used encoding method produces box-characters because the control characters in it are not a part of these fonts. For example if I encode "123456" with the program I mentioned, it'll give out "Í,BXLÎ" and that works fine with the external Code128 font. But it does not work with the ones Windows 7 comes with, they show up as "[](proper bars)[]", or "Í(proper bars)Î". The start and stop characters are replaced with boxes or left as they are because they don't exist as proper bars for the font. what the deal is with the Windows 7's built-in Code128 fonts? Why do they use different control characters for other fonts of the same format? Can anyone figure out how to get a readable and proper barcode for example in Excel with the built-in Code128 fonts?
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Mar 11, 2010
I'm building an application that reads barcode scanning data into multiple forms and textboxes. At the moment, to handle that data I have created a large nested if statement that checks to see which object has focus so that the scanned data is placed there and focus moves down to the next object:
Private Sub HandleData(ByVal TheReaderData As Symbol.Barcode.ReaderData)
'Scanning Data into frmGetCount
If frmName.Name = "frmGetCount" Then
[code].....
This is just for one of 5 forms I am currently developing. I am looking for a way to make this code much more dynamic and re-usable by removing the hard-coded objects name
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Nov 8, 2011
I've easily found various QR-Code generators, but I need to use the data stored in the barcode on a regular desktop app using VB.Net and a WebCam or eventually an flash, javascript webpage to do the job.
Should there be an online service for this? Maybe a flash app?
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Aug 28, 2009
I am developing a Winforms application which read barcode from barcode scanner. It's an Human wedge scanner. This will work if I placed the cursor in any textbox or notepad. But i don't want like that. Reason is that it's cordless scanner. If some want to scan some thing in store they will move around, so there is possibility of screen saver coming or system gets locked if that happens the barcodes wont capture, but the user who is scanning the barcodes won't know this thing.
So i am reading the data using serial port communication and my scanner sending the data character by character, Not a whole string. so for that I wrote the following code. Thsi code will works if i am writing to any textbox. But it is not working if want to store it in any global string. Only first character is storing in the string. The below code is working perfectly fine. but if want to save the string in Global String variable instaed of textbox the only first character in the string is storing.
[Code]...
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Apr 26, 2011
Im using VB2008... Net framework 3.0. Basically I have a barcode scanner that is sending the software data...Everything is working fine if I interface the scanner as a keyboard wedge and set the scanner suffix as 'Enter'...In the software I have an event handler on keypress.down...
If keycode.Enter then
.....
.....
....
etc.
However as a RS232 interface I cant get the same result? Hyper terminal reads it perfectly. I've tried all the keypress options but it doesnt work (I assume because it's not actually a key press). when the textbox recieves the CR/LF from RS232? The scanner that does keyboard wedge interfacing is not an option as it is far too expensive for my project.
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Nov 27, 2010
I'm mohammed from Oman ,I'm visual studio.net programmer How I can Read the Data From Barcode Weight scales By Serial port and TcpIp port
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Nov 16, 2011
I am at a bit of a loss at the moment. What I am basically writing is the password elements of a membership system. What I do is generate a random salt value, take the registered password, combine the two and then pass the new string through a function which will generate a SHAManaged 512 hash.
I then convert the hash and salt string into Byte arrays and store these in my database.The problem comes when I then compare a login attempt against the original value I am being supplied with a completely different hash for the password being presented by the user, even though it should be exactly the same.
Here is my code when someone registers their new account:
[Code]...
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Aug 3, 2010
[Code]...
The garbage collector in .NET moves objects, so the object's address is not stable. How is Object's GetHashCode() method implemented?
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Dec 1, 2010
I have an openfiledialog, I show the dialog and the user selects there file. How could I calculate the MD5 hash of the OFD.filename/file opened? Or calculate the SHA1, what ever is easiest.
PS: This is in Visual basic 2010 Express.
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Nov 7, 2010
I know MD5 hashes have been asked about 1000+ times, but this question is slightly different.I am looking to find the true MD5 hash of an image, but without using a string for the file's location. I am looking to be able to call on the image inside of a picturebox rather than somewhere on my computer or the internet.
For example, I want to find the MD5 hash of an image inside of my picturebox.
If this doesn't make sense, please ask any questions you may have.
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Dec 26, 2010
im creating a simple login / registrate form in visual studio 2008 anplant Hash and salt to my login and registrate forms, im using mysql to connect to a online mysql serverthis is my codes i ahve now
Form 1 - Login
Try
DB_Connect = New MySqlConnection()
[code].....
i really need this working, all works but nothing is encrypted
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Feb 6, 2012
I have a page with a URL that includes a hash value (www.mysite.com/#123).What I want to do is use that value to determine what is displayed on the page - much like using a querystring.I am using the hash value because the content on the page can be changed client side (I am avoiding page reloads where possible) - if the user then links to another page and uses the back button to return, I need to use the hash value to display the page as it was when they left it.So I'm looking for an if statement that will look something like this:
[code]...
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Mar 21, 2009
I would like to write a function GetHashCodeOfList() which returns a hashcode of a list of strings regardless of order. Given 2 lists with the same strings should return the same hashcode.
ArrayList list1 = new ArrayList()
list1.Add("String1");
list1.Add("String2");
[Code].....
I can first sort the list, then combine the sorted list into 1 long string and then call GetHashCode(). However sorting is a slow operation. I can get the hash of each individual string (by calling string.GetHashCode()) in the list, then multiplying all hashes and calling Mod UInt32.MaxValue. For Example: "String1".GetHashCode() * "String2".GetHashCode * ... MOD UInt32.MaxValue. But this results in a number overflow.
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Aug 10, 2009
I'm trying to figure out a way to compare two "salted-hash" strings. How can I do this? I know that the salt is a random generated value that's appended to the plain text, then we just compute the hash of that new string.So how can I compare these two values? O_O (The new hash that the user hash written in a textbox and the hash stored in a database)
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Apr 10, 2012
I have a function in VB.net that returns a password hash. I need to make a web interface to the same database and I'm not sure how to return the same hash in PHP. Does anyone know both languages enough to convert this to PHP?
Code:
Public Function GenerateHash(ByVal SourceText As String) As String
'Create an encoding object to ensure the encoding standard for the source text
Dim Ue As New UnicodeEncoding()
[Code].....
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Oct 1, 2010
I am using the following piece of code (where sId is a Unique Id in our system) to generate Unique Hash value of 16 characters Max in length
Dim oMD5Hash As System.Security.Cryptography.SHA1 = System.Security.Cryptography.SHA1.Create()
Dim sHash As String =
[Code].....
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Jun 7, 2012
I am having issues to hash with sha 1 salted in vb. I have an SMF forum and it uses SHA 1 salted to encrypt its passwords. I want to make a program which is only available to users who have registered in my forum so I have to create a login system in my program. The problem is that how do I hash to SHA 1 salted in vb?I have explained what I want to do a bit more in details below:User opens program >They login using their forum account details >Program hashes the PASSWORD the user has entered to SHA 1 salted >The program then connects with the forum's database and compares the password value > (The Username is checked first tho)
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Dec 18, 2011
The code below allows a user to enter user name and password to log in to enter marks of students. SQL data reader verifies the user credentials from the database before authentication takes place. modify the code by salting and hashing the password.
Dim frm As New MarksEntryFrm
Dim flag As Boolean
flag = False
[Code]....
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Apr 1, 2011
I am porting over some code from .net (vb) to php and I came across some md5 hashing that I can't reproduce in php. In the .net one there are two functions one uses UTF-8 encoding and the other uses Unicode encoding. The output is a different hash when passed in a string
// First function (returns GUID)
Dim oHasher As Cryptography.MD5 = Cryptography.MD5.Create()
Dim oEncoder As New System.Text.UTF8Encoding()
Dim csData() As Byte
[Code]...
but they both produce the same result. Is it possible to produce the same results in php with md5 hashing?
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Jul 19, 2011
How do I retrieve a hash value when the value itself is an object.I am giving an example here
dim ht as new hastable
dim person as clsperson
ht.add(0, new ("AAA", "16", "23425345")
ht.add(1, new("BBB", "18", "464745756")
[code]....
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Apr 21, 2012
PLATFORM VERSION INFO
Windows : 5.1.2600.131072 (Win32NT)
Common Language Runtime : 2.0.50727.1433
[code]....
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May 29, 2009
I was asked by an employer to sort a hash table. I always thought that the usage of a hash table was in a way non-sort friendly. Am I wrong in thinking this, and if not can you point me to a good VB.Net(Yes Kill me now, but it's an old system) method of sorting a hash table.
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