CRIPTOGRAFIA

... outros imports...
Imports System.Security
Imports System.Security.Cryptography
Imports System.IO
Imports System.Runtime.InteropServices
Imports System.Text.RegularExpressions
Imports System.Text

Public Class MyData
    Implements IDisposable

    [ô][ô][ô] <summary>
    [ô][ô][ô] Criptografa um texto.
    [ô][ô][ô] </summary>
    [ô][ô][ô] <param name=[Ô]plainText[Ô]>Texto á criptografar.</param>
    [ô][ô][ô] <returns>Texto criptografado.</returns>
    [ô][ô][ô] <example>
    [ô][ô][ô] <code>Dim strEncryptedText As String = Encrypt([Ô]MeuTexto[Ô])</code>
    [ô][ô][ô] </example>
    [ô][ô][ô] <remarks>Utiliza a Rjindael.</remarks>
    Public Function Encrypt(ByVal plainText As String) As String
        Dim passPhrase As String = [Ô]chavedecriptografia[Ô]
        Dim saltValue As String = [Ô]ValorDeSalto[Ô]
        Dim hashAlgorithm As String = [Ô]SHA1[Ô]
        Dim passwordIterations As Integer = 2
        Dim initVector As String = [Ô]@1B2c3D4e5F6g7H8[Ô] [ô]Veja que são 16 posições.
        Dim keySize As Integer = 256
        Dim initVectorBytes As Byte() = Encoding.ASCII.GetBytes(initVector)
        Dim saltValueBytes As Byte() = Encoding.ASCII.GetBytes(saltValue)
        Dim plainTextBytes As Byte() = Encoding.UTF8.GetBytes(plainText)
        Dim password As New PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations)
        Dim derivar As New Rfc2898DeriveBytes(passPhrase, saltValueBytes, passwordIterations)
        Dim keyBytes As Byte() = derivar.GetBytes(keySize \ CInt(8))
        Dim symmetricKey As New RijndaelManaged()
        symmetricKey.Mode = CipherMode.CBC
        Dim encryptor As ICryptoTransform = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes)
        Dim memoryStream As New MemoryStream()
        Dim cryptoStream As New CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write)
        cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length)
        cryptoStream.FlushFinalBlock()
        Dim cipherTextBytes As Byte() = memoryStream.ToArray()
        memoryStream.Close()
        cryptoStream.Close()
        Dim cipherText As String = Convert.ToBase64String(cipherTextBytes)
        Return cipherText
    End Function
    [ô][ô][ô] <summary>
    [ô][ô][ô] De-criptografa um texto criptografado com a Rjindael.
    [ô][ô][ô] </summary>
    [ô][ô][ô] <param name=[Ô]cipherText[Ô]>Texto criptografado.</param>
    [ô][ô][ô] <returns>Texto de-criptografado.</returns>
    [ô][ô][ô] <example>
    [ô][ô][ô] <code>Dim strDecrptedText As String = Decrypt(varTextoCriptografado)</code>
    [ô][ô][ô] </example>
    [ô][ô][ô] <remarks>Válido somente para as criptografias feitas com esta classe.</remarks>
    Public Function Decrypt(ByVal cipherText As String) As String
        Dim passPhrase As String = [Ô]chavedecriptografia[Ô]
        Dim saltValue As String = [Ô]ValorDeSalto[Ô]
        Dim hashAlgorithm As String = [Ô]SHA1[Ô]
        Dim passwordIterations As Integer = 2
        Dim initVector As String = [Ô]@1B2c3D4e5F6g7H8[Ô] [ô]Veja que são 16 posições.
        Dim keySize As Integer = 256
        Dim initVectorBytes As Byte() = Encoding.ASCII.GetBytes(initVector)
        Dim saltValueBytes As Byte() = Encoding.ASCII.GetBytes(saltValue)
        Dim cipherTextBytes As Byte() = Convert.FromBase64String(cipherText)
        Dim password As New PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations)
        Dim derivar As New Rfc2898DeriveBytes(passPhrase, saltValueBytes, passwordIterations)
        Dim keyBytes As Byte() = derivar.GetBytes(keySize \ 8)
        Dim symmetricKey As New RijndaelManaged()
        symmetricKey.Mode = CipherMode.CBC
        Dim decryptor As ICryptoTransform = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes)
        Dim memoryStream As New MemoryStream(cipherTextBytes)
        Dim cryptoStream As New CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read)
        Dim plainTextBytes As Byte() = New Byte(cipherTextBytes.Length - 1) {}
        Dim decryptedByteCount As Integer = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length)
        memoryStream.Close()
        cryptoStream.Close()
        Dim plainText As String = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount)
        Return plainText
    End Function
 ... a classe continua ...

   ...
   Dim cn As New MySqlcommand(ConfigurationManager.ConnectionStrings(0).ConnectionString)
   Dim mCommand As MySqlCommand = cn.CreateCommand;
   mCommand.CommandText = String.Format([Ô]INSERT INTO contatos (NOME, SENHA) ([ô]{0}[ô],[ô]{1}[ô])[Ô], txtNome.Text, MyData.Encrypt(txtSenha.Text))
   mCommand.ExecuteNonQuery
   ...

   ...
   Public Enum LoginResponses
      UserNotFound
      PassNotMatch
      Success
      None
   End Enum
   ...
   Dim ok As LoginResponses = LoginResponses.PassNotMatch
   Dim da As New MySqlDataAdapter(String.Format([Ô]SELECT NOME, SENHA FROM contatos WHERE NOME =[ô]{0}[ô], txtNome.Text,
                                                             ConfigurationManager.ConnectionStrings(0).ConnectionString)
   Dim tb As New DataTable([Ô]temp[Ô])
   da.Fill(tb)
   If (tb.Rows.Count = 0)
     ok = LoginResponses.UserNotFound
   Else
      For Each r As DataRow In tb.Rows
          If MyData.Decrypt(r([Ô]Senha[Ô])) = txtSenha.Text Then
               ok = LoginResponses.Success
               Exit For
          End If
      Next 
   End If
   ...