Cryptography

Hi all, yes I've got yet another 'problem'.

This time it is about encrypting data, not really decripting. I think I need the System.Security.Cryptography namespace, since that's the one they recomment at msdn.microsoft.com.

Well, all I want is to encode an input string using MD5 or DES and select the security strenght, or bits (128-bit or 256-bit). Then I want to respond the output string.

Like: Input > Proces > Response.Write(Output)

i'm using this for my encrypt password:

Imports System.Web.Security

I found working code (Rijndael Algorithm => Advanced Encryption Standard) which could interest you.

Let's start with the class =>  Crypto.vb

Imports System.IO
Imports System.Text
Imports System.ComponentModel
Imports System.Security.Cryptography

Public Class Crypto

    Public Function EncryptString(ByVal InputString As String, ByVal PassPhrase As String, Optional ByVal IVString As String = vbNullString) As String

        Dim CryptProvider As New RijndaelManaged()
        Dim hashMD5 As New MD5CryptoServiceProvider()
        Dim InputbyteArray() As Byte = Encoding.UTF8.GetBytes(InputString)

        CryptProvider.Key = hashMD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(PassPhrase) )
        CryptProvider.IV = hashMD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(IVString))
        CryptProvider.Mode = CipherMode.CBC

        Dim ms As MemoryStream = New MemoryStream()
        Dim cs As CryptoStream = New CryptoStream(ms, _
        CryptProvider.CreateEncryptor(), CryptoStreamMode.Write)
        cs.Write(InputbyteArray, 0, InputbyteArray.Length)
        cs.FlushFinalBlock()

        Dim ret As StringBuilder = New StringBuilder()
        Dim b() As Byte = ms.ToArray
        Dim I As Integer
        Dim Out As String
        For I = 0 To UBound(b)
             'Format as hex
             ret.AppendFormat("{0:X2}", b(I))
        Next
        Return ret.ToString()

    End Function

    Public Function DecryptString(ByVal InputString As String, ByVal PassPhrase As String, ByVal IVString As String) As String

        Dim DES As New RijndaelManaged()

        Dim hashMD5 As New MD5CryptoServiceProvider()

        DES.Key = hashMD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(PassPhrase) )
        DES.IV = hashMD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(IVString))
        DES.Mode = CipherMode.CBC
        'Put the input string into the byte array
        Dim inputByteArray(InputString.Length / 2 - 1) As Byte
        Dim X As Integer
        For X = 0 To InputString.Length / 2 - 1
             Dim IJ As Integer = (Convert.ToInt32(InputString.Substring(X * 2, 2), 16))
             Dim BT As New ByteConverter()
             inputByteArray(X) = New Byte()
             inputByteArray(X) = BT.ConvertTo(IJ, GetType(Byte))
        Next

        'Create the crypto objects
        Dim MS As MemoryStream = New MemoryStream()
        Dim CS As CryptoStream = New CryptoStream(MS, DES.CreateDecryptor(), CryptoStreamMode.Write)

        'Flush the data through the crypto stream into the memory stream
        CS.Write(inputByteArray, 0, inputByteArray.Length)
        CS.FlushFinalBlock()

        'Get the decrypted data back from the memory stream
        Dim ret As StringBuilder = New StringBuilder()
        Dim B() As Byte = MS.ToArray
        Dim I As Integer
        For I = 0 To UBound(B)
             ret.Append(Chr(B(I)))
        Next
        Return ret.ToString()

    End Function

End Class

Then create an other page whatever.aspx, create an instance of our Crypto class
and use the 2 functions of that Crypto class for encrypt and decrypt your string:

Sub Page_Load(.................

Dim Crypt As New Crypto()
Dim TestString, PassPhrase, IVPhrase, CryptString, DecryptString As String
TestString = "Testing"
PassPhrase = "This is a passphrase"
IVPhrase = "This is an IV phrase"

Response.Write("Original String: " & TestString & "<br />")

CryptString = Crypt.EncryptString(TestString, PassPhrase, IVPhrase)
Response.Write("EnCrypt String: " & CryptString & "<br />")

DecryptString = Crypt.DecryptString(CryptString, PassPhrase, IVPhrase)
Response.Write("DeCrypt String: " & DecryptString & "<br />")

End Sub