An Application Package on Data Encryption and Decryption ~~ VisualBasic Code Snippet + GUI Design

In cryptography, a substitution cipher is a method of  encoding by which units of plaintext are replaced with ciphertext, according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing an inverse substitution.

There are a number of different types of substitution cipher. If the cipher operates on single letters, it is termed a simple substitution cipher; a cipher that operates on larger groups of letters is termed polygraphic. A monoalphabetic cipher uses fixed substitution over the entire message, whereas a polyalphabetic cipher uses a number of substitutions at different positions in the message, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext and vice versa. http://en.wikipedia.org/wiki/Substitution_cipher

** Click here for 3DES (Data Encryption & Decryption)

Shown below is the screen shot and source code for each module respectively of a data encryption and decryption system using simple substitution cipher.

Screen shot for 'Start Page'
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Source code for 'Start Page'
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Public Class Start_Page

    Private Sub encrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles encrypt.Click

        frmEncrypt.ShowDialog()

    End Sub

    Private Sub Start_Page_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize

        Me.Height = 357

        Me.Width = 634

    End Sub

    Private Sub decrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles decrypt.Click

        frmDecrypt.ShowDialog()

    End Sub

    Private Sub exitt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles exitt.Click

        Me.Close()

    End Sub

End Class

Screen shot for 'frmEncrypt'
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Source code for 'frmEncrypt'
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Public Class frmEncrypt

    Private Sub cmdopen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdopen.Click

        ofd.ShowDialog()

        txtfilename.Text = ofd.FileName

        Try

            txtoriginal.Text = My.Computer.FileSystem.ReadAllText(ofd.FileName)

        Catch ex As Exception  ' Bad practice (catching exception)

            Dim a As String

            a = MessageBox.Show("File not found, Check the file name and try again", "Encryption", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

            cmdopen.Focus()

            txtfilename.Text = String.Empty

        End Try

    End Sub

    Private Sub cmdsaveencrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdsaveencrypt.Click

        If txtEncrypted.Text = String.Empty Then

            Dim a As String

            a = MessageBox.Show("File not found; Check to make sure the file has been encrypted", "Encryption", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

            cmdopen.Focus()

        Else

            Dim inn As String

            inn = InputBox("Enter file name")

            If inn = "" Then

            Else

                System.IO.File.WriteAllText("'" & inn & " ' ", txtEncrypted.Text)

                Dim haha As String

                haha = MessageBox.Show("File saved", "Encryption", MessageBoxButtons.OK, MessageBoxIcon.Information)

                txtEncrypted.Text = String.Empty

                txtoriginal.Text = String.Empty

                txtfilename.Text = ""

            End If

          End If

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdencrypt.Click

        Try

            txtEncrypted.Text = My.Computer.FileSystem.ReadAllText(ofd.FileName).ToLower.Replace("a", "/").Replace("b", "\").Replace("c", "*").Replace("d", "-").Replace("e", "+").Replace("f", "^").Replace("g", "<").Replace("h", ">").Replace("i", "!").Replace("j", "~").Replace("k", "@").Replace("l", "#").Replace("m", "$").Replace("n", "%").Replace("o", "&").Replace("p", "(").Replace("q", ")").Replace("r", "{").Replace("s", "}").Replace("t", "[").Replace("u", "]").Replace("v", "=").Replace("w", "'").Replace("x", "`").Replace("y", ";").Replace("z", ":").Replace("1", "|").Replace("2", "_")

            '-------substitution area--a.k.a replacement cipher------

       

        Catch ex As Exception

            Dim w As String

            w = MessageBox.Show("Check to make sure a file is selected", "Encryption", MessageBoxButtons.OK, MessageBoxIcon.Information)

            cmdopen.Focus()

        End Try

    End Sub

  

    Private Sub cmdclose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdclose.Click

        Me.Close()

    End Sub

    Private Sub frmEncrypt_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize

        Me.Height = 534

        Me.Width = 970

    End Sub

    Private Sub cmdclear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdclear.Click

        txtoriginal.Text = ""

        txtEncrypted.Text = ""

        txtfilename.Text = ""

        cmdopen.Focus()

    End Sub

    Private Sub frmEncrypt_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

End Class

Screen shot for 'frmDecrypt'
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Source code  for 'frmDecrypt'
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Public Class frmDecrypt

    Private Sub cmdopen_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdopen.Click

        Try

            OpenFileDialog1.ShowDialog()

            txtfilename.Text = OpenFileDialog1.FileName

            txtoriginal.Text = My.Computer.FileSystem.ReadAllText(OpenFileDialog1.FileName)

        Catch ju As Exception

            Dim viva As String

            viva = MessageBox.Show("No file selected", "Decryption", MessageBoxButtons.OK, MessageBoxIcon.Information)

            cmdopen.Focus()

            txtfilename.Clear()

        End Try

    End Sub

    Private Sub cmddecrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmddecrypt.Click

        If txtoriginal.Text = "" Then

            Dim viv As String

            viv = MessageBox.Show("No file selected for decryption", "Decryption", MessageBoxButtons.OK, MessageBoxIcon.Information)

        Else

            txtdecrypted.Text = My.Computer.FileSystem.ReadAllText(OpenFileDialog1.FileName).ToLower.Replace("/", "a").Replace("\", "b").Replace("*", "c").Replace("-", "d").Replace("+", "e").Replace("^", "f").Replace("<", "g").Replace(">", "h").Replace("!", "i").Replace("~", "j").Replace("@", "k").Replace("#", "l").Replace("$", "m").Replace("%", "n").Replace("&", "o").Replace("(", "p").Replace(")", "q").Replace("{", "r").Replace("}", "s").Replace("[", "t").Replace("]", "u").Replace("=", "v").Replace("'", "w").Replace("`", "x").Replace(";", "y").Replace(":", "z").Replace("|", "1").Replace("_", "2")

            '--.....decryption arena....don't touch--------------------------------

        End If

    End Sub

    Private Sub cmdexit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdexit.Click

        Me.Close()

    End Sub

    Private Sub frmDecrypt_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize

        Me.Height = 534

        Me.Width = 970

    End Sub

    Private Sub cmdsavedecrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdsavedecrypt.Click

        If txtdecrypted.Text = String.Empty Then

            Dim a As String

            a = MessageBox.Show("File not found", "Decryption", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

            cmdopen.Focus()

        Else

            Dim oops As String

            oops = InputBox("Enter file name")

            If oops = "" Then

' Do nothing

            Else

                System.IO.File.WriteAllText("'" & oops & " ' ", txtdecrypted.Text)

                Dim ha As String

                ha = MessageBox.Show("File saved", "Decryption", MessageBoxButtons.OK, MessageBoxIcon.Information)

                txtdecrypted.Text = String.Empty

                txtoriginal.Text = String.Empty

                txtfilename.Text = ""

                'GoTo k

            End If

        End If

    End Sub

    Private Sub btnclear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnclear.Click

        txtoriginal.Text = ""

        txtdecrypted.Text = ""

        txtfilename.Text = ""

        cmdopen.Focus()

    End Sub

End Class
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