Programming Forums > Application Development > Visual Basic .NET

Intimidat0r · Jul 8th, 2005, 5:03 PM

I have tried to make a program to decrypt simple ROT decryptions which is where if it's like ROT 4 you move each letter 4 spaces down, so A becomes E, W becomes Z and so on. Here is my code:

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    Dim ROTIndex As Integer
    Dim Encrypted As String
    Dim Decrypted() As String = ""

    Sub Main()
        Console.WriteLine("Rotation index: ")
        ROTIndex = Console.ReadLine()
        Console.WriteLine("Encrypted text: ")
        Encrypted = Console.ReadLine()
        For Index As Integer = 0 To Encrypted.Length
            Decrypted = Decrypted & Chr(Asc(Encrypted.Substring(Index, 1) + 13))
        Next
        Console.WriteLine("Decrypted Text: " & Decrypted)
    End Sub

It looks all well and good but when I try to run it I get a bug saying "Invalid cast exception -> cast from string "h" to type 'Double' is not valid" and it says it's occurring on the line that says this:

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Decrypted = Decrypted & Chr(Asc(Encrypted.Substring(Index, 1) + 13))

Does anybody know why it may be doing this?

Rory · Jul 8th, 2005, 9:12 PM

Your adding 13 (byte) to a character which should work as they are actually the same thing but no in VB's universe.

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Chr(Asc(Encrypted.Substring(Index, 1)) + 13)

For some reason VB's so Unicodified (Grrr! English IS the only language in the world). This works though:

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    Dim ROTIndex As Byte
    Dim Buffer As Char()

    Sub Main()
        Console.Write("Rotation index: ")
        ROTIndex = Console.ReadLine()

        Console.Write("Encrypted text: ")
        Buffer = Console.ReadLine()

        For Index As Integer = Buffer.GetLowerBound(0) To Buffer.GetUpperBound(0)
            Buffer(Index) = Chr(Asc(Buffer(Index)) + ROTIndex)
        Next

        Console.WriteLine("Decrypted Text: " & Buffer)

        Console.ReadLine()
    End Sub

Jul 8th, 2005, 5:03 PM	#1
Intimidat0r Hobbyist Programmer Join Date: May 2005 Location: Don't know, but the padded walls are a nice touch. Posts: 126 Rep Power: 0	ROT Decryptor I have tried to make a program to decrypt simple ROT decryptions which is where if it's like ROT 4 you move each letter 4 spaces down, so A becomes E, W becomes Z and so on. Here is my code: (Toggle Plain Text) Dim ROTIndex As Integer Dim Encrypted As String Dim Decrypted() As String = "" Sub Main() Console.WriteLine("Rotation index: ") ROTIndex = Console.ReadLine() Console.WriteLine("Encrypted text: ") Encrypted = Console.ReadLine() For Index As Integer = 0 To Encrypted.Length Decrypted = Decrypted & Chr(Asc(Encrypted.Substring(Index, 1) + 13)) Next Console.WriteLine("Decrypted Text: " & Decrypted) End Sub Dim ROTIndex As Integer Dim Encrypted As String Dim Decrypted() As String = "" Sub Main() Console.WriteLine("Rotation index: ") ROTIndex = Console.ReadLine() Console.WriteLine("Encrypted text: ") Encrypted = Console.ReadLine() For Index As Integer = 0 To Encrypted.Length Decrypted = Decrypted & Chr(Asc(Encrypted.Substring(Index, 1) + 13)) Next Console.WriteLine("Decrypted Text: " & Decrypted) End Sub It looks all well and good but when I try to run it I get a bug saying "Invalid cast exception -> cast from string "h" to type 'Double' is not valid" and it says it's occurring on the line that says this: (Toggle Plain Text) Decrypted = Decrypted & Chr(Asc(Encrypted.Substring(Index, 1) + 13)) Decrypted = Decrypted & Chr(Asc(Encrypted.Substring(Index, 1) + 13)) Does anybody know why it may be doing this? __________________ Children in the dark cause accidents, and accidents in the dark cause children. http://www.ronincoders.org

Jul 8th, 2005, 9:12 PM	#2
Rory Expert Programmer Join Date: Jan 2005 Location: London Posts: 542 Rep Power: 4	Your adding 13 (byte) to a character which should work as they are actually the same thing but no in VB's universe. (Toggle Plain Text) Chr(Asc(Encrypted.Substring(Index, 1)) + 13) Chr(Asc(Encrypted.Substring(Index, 1)) + 13) For some reason VB's so Unicodified (Grrr! English IS the only language in the world). This works though: (Toggle Plain Text) Dim ROTIndex As Byte Dim Buffer As Char() Sub Main() Console.Write("Rotation index: ") ROTIndex = Console.ReadLine() Console.Write("Encrypted text: ") Buffer = Console.ReadLine() For Index As Integer = Buffer.GetLowerBound(0) To Buffer.GetUpperBound(0) Buffer(Index) = Chr(Asc(Buffer(Index)) + ROTIndex) Next Console.WriteLine("Decrypted Text: " & Buffer) Console.ReadLine() End Sub Dim ROTIndex As Byte Dim Buffer As Char() Sub Main() Console.Write("Rotation index: ") ROTIndex = Console.ReadLine() Console.Write("Encrypted text: ") Buffer = Console.ReadLine() For Index As Integer = Buffer.GetLowerBound(0) To Buffer.GetUpperBound(0) Buffer(Index) = Chr(Asc(Buffer(Index)) + ROTIndex) Next Console.WriteLine("Decrypted Text: " & Buffer) Console.ReadLine() End Sub

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Programming Forums > Application Development > Visual Basic .NET

ROT Decryptor