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Imports System.IO
Imports System.Text
Imports System.Security.Cryptography
Imports System.IO.Directory
    Private Function CreateKey(ByVal strPassword As String) As Byte()
        Dim bytKey As Byte()
        Dim bytSalt As Byte() = System.Text.Encoding.ASCII.GetBytes("yourstring")
        Dim pdb As New Rfc2898DeriveBytes(strPassword, bytSalt)

        bytKey = pdb.GetBytes(32)

        Return bytKey 'Return the key.
    End Function

    Private Function CreateIV(ByVal strPassword As String) As Byte()
        Dim bytIV As Byte()
        Dim bytSalt As Byte() = System.Text.Encoding.ASCII.GetBytes("yourstring")
        Dim pdb As New Rfc2898DeriveBytes(strPassword, bytSalt)

        bytIV = pdb.GetBytes(16)

        Return bytIV 'Return the IV.
    End Function

    Private Sub EncryptTextToFile(ByVal Data As String, ByVal FileName As String)
        Dim key() As Byte = CreateKey("anotherstring")
        Dim IV() As Byte = CreateIV("yetsanotherstring")
        Try
            ' Create or open the specified file.
            Dim fStream As FileStream = File.Open(FileName, FileMode.Create)

            ' Create a new Rijndael object.
            Dim RijndaelAlg As Rijndael = Rijndael.Create

            ' Create a CryptoStream using the FileStream 
            ' and the passed key and initialization vector (IV).
            Dim cStream As New CryptoStream(fStream, RijndaelAlg.CreateEncryptor(key, IV), CryptoStreamMode.Write)

            ' Create a StreamWriter using the CryptoStream.
            Dim sWriter As New StreamWriter(cStream)

            Try
                ' Write the data to the stream 
                ' to encrypt it.
                sWriter.WriteLine(Data)
            Catch e As Exception
                MessageBox.Show(e.Message, "An error occurred", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Finally
                ' Close the streams and
                ' close the file.
                sWriter.Close()
                cStream.Close()
                fStream.Close()
            End Try
        Catch e As CryptographicException
            MessageBox.Show(e.Message, "A Cryptographic error occurred", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Catch e As UnauthorizedAccessException
            MessageBox.Show(e.Message, "A file error occurred", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub

    Private Function DecryptTextFromFile(ByVal FileName As String) As String
        Dim key() As Byte = CreateKey("anotherstring")
        Dim IV() As Byte = CreateIV("yetanotherstring")
        Try
            ' Create or open the specified file. 
            Dim fStream As FileStream = File.Open(FileName, FileMode.OpenOrCreate)

            ' Create a new Rijndael object.
            Dim RijndaelAlg As Rijndael = Rijndael.Create

            ' Create a CryptoStream using the FileStream 
            ' and the passed key and initialization vector (IV).
            Dim cStream As New CryptoStream(fStream, RijndaelAlg.CreateDecryptor(key, IV), CryptoStreamMode.Read)

            ' Create a StreamReader using the CryptoStream.
            Dim sReader As New StreamReader(cStream)

            ' Read the data from the stream 
            ' to decrypt it.
            Dim val As String = Nothing

            Try
                val = sReader.ReadLine()
            Catch e As Exception
                MessageBox.Show(e.Message, "An Cerror occurred", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Finally
                ' Close the streams and
                ' close the file.
                sReader.Close()
                cStream.Close()
                fStream.Close()
            End Try
            ' Return the string. 
            Return val

        Catch e As CryptographicException
            MessageBox.Show(e.Message, "A Cryptographic error occurred", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Return Nothing
        Catch e As UnauthorizedAccessException
            MessageBox.Show(e.Message, "A file error occurred", MessageBoxButtons.OK, MessageBoxIcon.Error)
            Return Nothing
        End Try
    End Function