[RESOLVED] Self Validating Number Generation

[wrack]

Hi,

Been a while since I have been here. I will rather jump to the point then chit chatting.

I need to create a self validating number. Does anyone here has an experience to create an algorithm to achieve such things? What sort of base data is required? e.g. Seed value which is used to generate a number or something like that.

Basicall I need to create a barcode number for users so they can scan the barcode rather than entring the username everytime (basically for auditing and tracing of files purposes).

So what I would like to do is create a unique barcode for each user that can be printed but upon scan the an application on the PDA Scanner should be able to varify that the number indeed is the correct one before sending it to the server for the database verification. This is much like Credit Card or Social Security Number or ABN/ACN/TFN (for those who live in Australia).

Does this all make any sense? Please let me know if anymore information is required.

Cheers

[Dnereb]

Is there a maximum name length in your situation?
If not can that be made a requirement?
Else it would be near impossible to keep te encryption fixed

And that's the clue, you need to look for encryption anyways

[wrack]

I can make it maximum 12 characters if that is helpful?

[Dnereb]

Sure,

Now think about this:

the alfabet in lowercase and a few extra characters like whitespace
can be contained in 32 diffrent numbers
0-31.
You need 6 bits for this.
convert your string into a continious bit stream and
this into a decimal number

If you heve some patience I will make an example tonight (GMT +1)

[wrack]

Hi there,

Thanks for the suggestion. Yeah I wouldn't mind looking at the example. At the moment I am taking a given date as a decimal value in SQL Server. Then getting a GUID and retrieving the ASCII of each character in the GUID and then adding it up and then finally multiplying the that number to the decimal value of the datetime.

Then I need to do something to convert that nice looking decimal number to 8 - 12 character.

Let's see how you are thinking about doing it?

[Dnereb]

Whilst writing it I Realized 5 bits per character would do.

Make a windows project with a Form => Form1
3 textboxes => TextBox1 to 3
And a Button => button1

Place the code in the form and enter a string in Textbox1

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim BinaryString As String = String.Empty
        Dim Ch() As Char
        'Convert the input
        Ch = Me.TextBox1.Text.PadLeft(12, " ")
        For Counter As Integer = 0 To Ch.Length - 1
            BinaryString &= ReduceTo6BitString(Ch(Counter))
        Next
        'Display the output
        Me.TextBox2.Text = BinaryString.Length
        Me.TextBox3.Text = Convert.ToInt64(BinaryString, 2).ToString 

    End Sub
    ''' <summary>
    ''' Reduce input to upper chars or whitespace
    ''' </summary>
    ''' <param name="sender"></param>
    ''' <param name="e"></param>
    ''' <remarks></remarks>
    Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Char.IsLetter(e.KeyChar) Then
            e.KeyChar = Char.ToUpper(e.KeyChar)
        ElseIf Not (Char.IsWhiteSpace(e.KeyChar) Or Char.IsControl(e.KeyChar)) Then
            e.Handled = True
        End If

    End Sub
    ''' <summary>
    ''' Convert the input to "Binary" strings with a length of 5
    ''' </summary>
    ''' <param name="Ch"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Function ReduceTo6BitString(ByVal Ch As Char) As String
        Dim CharValue As Integer

        If Char.IsWhiteSpace(Ch) Then
            ReduceTo6BitString = "00000"
        Else
            CharValue = Asc(Ch) - 64
            ReduceTo6BitString = Convert.ToString(CharValue, 2).PadLeft(5, "0")

        End If

    End Function


End Class

Have Fun!

[wrack]

Hey Dnereb, thanks for the quick solution code and your efforts.

Cheers

[Dnereb]

Thx! i realy appriciate feedback on my efforts!

BTW I just notice you're an Aussie, i'll be in Sydney and albury in october

if you do know any vacancies for a .Net programmer....

See Ya!