Imports System.IO
Imports System.Security
Imports System.Security.Cryptography
Imports System.Runtime.InteropServices
Imports System.Text
Public Class Form1
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
 
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        ' Must be 64 bits, 8 bytes.
        ' Distribute this key to the user who will decrypt this file.
        Dim sSecretKey As String
        sSecretKey = CSEncryptDecrypt.Class1.GenerateKey() ' Get the Key for the file to Encrypt.
        Dim gch As GCHandle = GCHandle.Alloc(sSecretKey, GCHandleType.Pinned)                       ' For additional security Pin the key.
        CSEncryptDecrypt.Class1.EncryptFile("C:\Prueba\Texto.txt", "C:\Prueba\TextoEncrypt.txt", sSecretKey)        ' Encrypt the file.        
        CSEncryptDecrypt.Class1.ZeroMemory(gch.AddrOfPinnedObject(), CType(sSecretKey.Length * 2, IntPtr))
        gch.Free()
    End Sub
 
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        ' Must be 64 bits, 8 bytes.
        ' Distribute this key to the user who will decrypt this file.
        Dim sSecretKey As String
        sSecretKey = CSEncryptDecrypt.Class1.GenerateKey() ' Get the Key for the file to Encrypt.
        Dim gch As GCHandle = GCHandle.Alloc(sSecretKey, GCHandleType.Pinned)
        CSEncryptDecrypt.Class1.DecryptFile("C:\Prueba\TextoEncrypt.txt", "C:\Prueba\Decrypt.txt", sSecretKey)    ' Decrypt the file.
        CSEncryptDecrypt.Class1.ZeroMemory(gch.AddrOfPinnedObject(), CType(sSecretKey.Length * 2, IntPtr)) ' Remove the Key from memory. 
        gch.Free()
    End Sub
End Class
 
 
Namespace CSEncryptDecrypt
 
    Class Class1
        <DllImport("kernel32.dll")> _
        Public Shared Sub ZeroMemory(ByVal addr As IntPtr, ByVal size As IntPtr)
        End Sub
        '  Call this function to remove the key from memory after use for security
        '<System.Runtime.InteropServices.DllImport("KERNEL32.DLL", EntryPoint:="RtlZeroMemory")> _
        'Public Shared Function ZeroMemory(Destination As IntPtr, Length As Integer) As Boolean
        'End Function
 
        ' Function to Generate a 64 bits Key.
        Public Shared Function GenerateKey() As String
            ' Create an instance of Symetric Algorithm. Key and IV is generated automatically.
            Dim desCrypto As DESCryptoServiceProvider = DirectCast(DESCryptoServiceProvider.Create(), DESCryptoServiceProvider)
 
            ' Use the Automatically generated key for Encryption. 
            Return ASCIIEncoding.ASCII.GetString(desCrypto.Key)
        End Function
 
        Public Shared Sub EncryptFile(sInputFilename As String, sOutputFilename As String, sKey As String)
            Dim fsInput As New FileStream(sInputFilename, FileMode.Open, FileAccess.Read)
 
            Dim fsEncrypted As New FileStream(sOutputFilename, FileMode.Create, FileAccess.Write)
            Dim DES As New DESCryptoServiceProvider()
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey)
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey)
            Dim desencrypt As ICryptoTransform = DES.CreateEncryptor()
            Dim cryptostream As New CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write)
 
            Dim bytearrayinput As Byte() = New Byte(CInt(fsInput.Length - 1)) {}
            fsInput.Read(bytearrayinput, 0, bytearrayinput.Length)
            cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length)
            cryptostream.Close()
            fsInput.Close()
            fsEncrypted.Close()
        End Sub
 
        Public Shared Sub DecryptFile(sInputFilename As String, sOutputFilename As String, sKey As String)
            Dim DES As New DESCryptoServiceProvider()
            'A 64 bit key and IV is required for this provider.
            'Set secret key For DES algorithm.
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey)
            'Set initialization vector.
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey)
 
            'Create a file stream to read the encrypted file back.
            Dim fsread As New FileStream(sInputFilename, FileMode.Open, FileAccess.Read)
            'Create a DES decryptor from the DES instance.
            Dim desdecrypt As ICryptoTransform = DES.CreateDecryptor()
            'Create crypto stream set to read and do a 
            'DES decryption transform on incoming bytes.
            Dim cryptostreamDecr As New CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read)
            'Print the contents of the decrypted file.
            Dim fsDecrypted As New StreamWriter(sOutputFilename)
            fsDecrypted.Write(New StreamReader(cryptostreamDecr).ReadToEnd())
            fsDecrypted.Flush()
            fsDecrypted.Close()
        End Sub
 
 
    End Class
End Namespace

Imports System.Security.AccessControl
Imports System.IO
 
 
Public Class Form1
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
 
 
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim FolderBrowserDialog1 As New FolderBrowserDialog
        With FolderBrowserDialog1
            If .ShowDialog() = DialogResult.OK Then
                TextBox1.Text = .SelectedPath
            End If
        End With
 
    End Sub
 
    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
        Dim fs As FileSystemSecurity = File.GetAccessControl(TextBox1.Text)
        fs.AddAccessRule(New FileSystemAccessRule(Environment.UserName, FileSystemRights.FullControl, AccessControlType.Deny))
        File.SetAccessControl(TextBox1.Text, CType(fs, FileSecurity))
    End Sub
 
    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
        Dim fs As FileSystemSecurity = File.GetAccessControl(TextBox1.Text)
        fs.RemoveAccessRule(New FileSystemAccessRule(Environment.UserName, FileSystemRights.FullControl, AccessControlType.Deny))
        File.SetAccessControl(TextBox1.Text, CType(fs, FileSecurity))
    End Sub
End Class