Basic Encryption

Hi

how do i convert

a b c d e f g h i j k l m n o p q r s t u v w x y z

to

x y z a b c d e f g h i j k l m n o p q r s t u v w

basically just going back 3 characters

so if i type "narmi" in the textbox and click a button i should get "kxojg"

i think!! :)

thanks

narmi2
LVL 1
narmi2Asked:
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Mike TomlinsonConnect With a Mentor Middle School Assistant TeacherCommented:
ah...duh...lol!

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim index As Integer
        Dim vals() As Char = "abcdefghijklmnopqrstuvwxyz".ToCharArray
        Dim input As New System.Text.StringBuilder(TextBox1.Text)
        For i As Integer = 0 To input.Length - 1
            index = Array.IndexOf(vals, input.Chars(i))
            If index <> -1 Then
                index = index - 3
                If index < 0 Then
                    index = vals.Length + index
                End If
                input.Chars(i) = vals(index)
            End If
        Next
        TextBox1.Text = input.ToString
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim index As Integer
        Dim vals() As Char = "abcdefghijklmnopqrstuvwxyz".ToCharArray
        Dim input As New System.Text.StringBuilder(TextBox1.Text)
        For i As Integer = 0 To input.Length - 1
            index = Array.IndexOf(vals, input.Chars(i))
            If index <> -1 Then
                index = index + 3
                If index > vals.GetUpperBound(0) Then
                    index = index - vals.Length
                End If
                input.Chars(i) = vals(index)
            End If
        Next
        TextBox1.Text = input.ToString
    End Sub
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gangwischCommented:
dim txt as string="abcd"

for i as integer=0 to origtxt.length-1
txt.chars(i)= asc(txt.chars(i))-3
'you will need to check if >80
next
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Mike TomlinsonMiddle School Assistant TeacherCommented:
Another way:

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim index As Integer
        Dim vals() As Char = "abcdefghijklmnopqrstuvwxyz".ToCharArray
        Dim input As New System.Text.StringBuilder(TextBox1.Text)
        For i As Integer = 0 To input.Length - 1
            index = Array.IndexOf(vals, input.Chars(i))
            If index <> -1 Then
                index = index - 3
                If index < 0 Then
                    index = vals.Length + index
                End If
                input.Chars(i) = vals(index)
            End If
        Next
        TextBox1.Text = input.ToString
    End Sub

This leaves any characters that are not "a-z" intact.
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narmi2Author Commented:
Idle Mind how would i reverse that?  so it does the opposite?
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Mike TomlinsonMiddle School Assistant TeacherCommented:
Define opposite?

You mean so that "abc" becomes "def"?
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narmi2Author Commented:
gangwisch - i get an error with your code saying "property char is read only"
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narmi2Author Commented:
idel mind,

i mean if i start off with "narmi" and click encrypt button, i get "kyojf"

then i want to click decrypt when "kyojf" is in the box which should give me "narmi" back again.
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narmi2Author Commented:
perfec :)
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Mike TomlinsonMiddle School Assistant TeacherCommented:
Written slightly more intelligently...

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox1.Text = Convert(TextBox1.Text, True)
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        TextBox1.Text = Convert(TextBox1.Text, False)
    End Sub

    Public Function Convert(ByVal str As String, ByVal Encrypt As Boolean) As String
        Dim index As Integer
        Dim vals() As Char = "abcdefghijklmnopqrstuvwxyz".ToCharArray
        Dim input As New System.Text.StringBuilder(str)
        For i As Integer = 0 To input.Length - 1
            index = Array.IndexOf(vals, input.Chars(i))
            If index <> -1 Then
                If Encrypt Then
                    index = index - 3
                    If index < 0 Then
                        index = vals.Length + index
                    End If
                Else
                    index = index + 3
                    If index > vals.GetUpperBound(0) Then
                        index = index - vals.Length
                    End If
                End If
                input.Chars(i) = vals(index)
            End If
        Next
        Return input.ToString
    End Function
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Mike TomlinsonMiddle School Assistant TeacherCommented:
If you want actual encryption (with a key that is) then see:
http://www.experts-exchange.com/Programming/Programming_Languages/Dot_Net/Q_21821682.html
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Mohamed ZedanCommented:
It's like this but first "narmi" encrypted is "kxojf"

 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim index As Integer
        Dim vals() As Char = "abcdefghijklmnopqrstuvwxyz".ToCharArray
        Dim input As New System.Text.StringBuilder(TextBox1.Text)
        For i As Integer = 0 To input.Length - 1
            index = Array.IndexOf(vals, input.Chars(i))
            If index <> -1 Then
                index = index + 3
                'If index < 0 Then
                '    index = vals.Length + index
                'End If
                if index > vals.length -1  then
                    index = index - vals.length
                end if
                input.Chars(i) = vals(index)
            End If
        Next
        TextBox1.Text = input.ToString
    End Sub

I deduced that it's only a matter of reversing the - to +
and checking for the opposite condition for index.
:)
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Mohamed ZedanCommented:
sorry i was too late :)
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