Encrypted DES format in ASP.Net
The .NET Framework also contains a TripleDES class, which is an improved version of
the old DES standard. TripleDES takes longer to encrypt and decrypt information,
but is much more secure than DES.
A Plain-Text Message Is Encrypted with the DES Algorithm Using a User-
Specified Password.
<%@ Import Namespace=”System.Security.Cryptography” %>
<%@ Import Namespace=”System.Text” %>
<script language=”VB” runat=”server”>
Dim aConstantIV() as Byte = _
{ &Haa, &Hbb, &Hcc, &Hdd, &Hee, &Hff, &H12, &H78 }
Sub btnSubmit_OnClick(source as Object, e as EventArgs)
Dim strEncryptedText as String = DESEncrypt(txtContents.Text)
lblResults.Text = “<b>Encrypted String:</b><xmp>” & _
strEncryptedText & “</xmp><p><i>” & _
“Copy this encrypted information to the clipboard! To decrypt“
& _
“it visit <a href=””Listing2.11.2.aspx””>Listing2.11.2.aspx</a>”
End Sub
Function GetKey(strPassword as String) as Byte()
‘Ensure that the strPassword string is at least 8 characters long
strPassword = strPassword.PadRight(9)
‘Now, convert the string into a byte array
Dim objUTF8 as New UTF8Encoding()
GetKey = objUTF8.GetBytes(strPassword.Substring(1, 8))
End Function
Function DESEncrypt(strEncrypt as String) as String
Dim aKey() as Byte
Dim objUTF8 as New UTF8Encoding()
‘Convert the password into a byte array
aKey = GetKey(txtPassword.Text)
‘Create an instance of the DES class
Dim objDES as DES = DES.Create()
objDES.Key = aKey
objDES.IV = aConstantIV
Convert the string into an array of bytes
Dim aByteData() as Byte = objUTF8.GetBytes(strEncrypt)
Dim objStreamEnc as SymmetricStreamEncryptor = objDES.CreateEncryptor()
Dim objCryptoStream as New CryptoMemoryStream()
objStreamEnc.SetSink(objCryptoStream)
objStreamEnc.Write(aByteData)
objStreamEnc.CloseStream()
Represent the byte array as a string
Dim i as Integer
Dim strTmp as String = “”
For i = 0 to objCryptoStream.Data.Length - 1
strTmp &= objCryptoStream.Data(i).ToString() & “ “
Next i
DESEncrypt = strTmp
End Function
</script>
<html>
<body>
<form runat=”server”>
<h1>Encrypt Information!</h1>
<b>Enter a Password:</b>
<asp:textbox id=”txtPassword” TextMode=”Password” runat=”server” />
<br><b>Enter text to encrypt:</b><br>
<asp:textbox id=”txtContents” TextMode=”MultiLine” runat=”server”
Columns=”50” Rows=”6” />
<br><asp:button id=”btnSubmit” runat=”server” Text=”Encrypt!”
OnClick=”btnSubmit_OnClick” />
<p>
<asp:label id=”lblResults” runat=”server” />
</form>
</body>
</html>
Recall that cryptography algorithms generally require two inputs: a key and the information to
be encrypted. The DES algorithm (as with many other symmetric algorithms) also require a
third input, an initialization vector (IV) that is used to get the encryption and decryption process started. This information, as well as the key, must be in the form of a Byte array.
