在網站使用Cookie或者存放數據到數據庫中的時候時常會用到加密解密，MD5非常好用，但是有的時候需要進行逆運算。那么此時DES對稱加密就比較好用了。設定一個密鑰，然后對所有的數據進行加密。代碼介紹如下，事先聲明僅為小弟個人理解，請各位多多指教
Imports System
Imports System.IO
Imports System.Text
Imports System.Diagnostics
Imports System.Security.Cryptography
Imports System.Text.RegularExpressions

'使用標準DES對稱加密
Public Function EncryptDes(ByVal SourceStr As String) As String

'get encodekey string from web.config
Dim skey As String
skey = ConfigurationSettings.AppSettings("EnCodeKey")

'put the input string into the byte array
Dim des As DESCryptoServiceProvider = New DESCryptoServiceProvider()
Dim inputByteArray As Byte()
inputByteArray = Encoding.Default.GetBytes(SourceStr)

'set encrypt object and skey
des.Key = ASCIIEncoding.ASCII.GetBytes(skey)
des.IV = ASCIIEncoding.ASCII.GetBytes(skey)
Dim ms As MemoryStream = New MemoryStream()
Dim cs As CryptoStream = New CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write)
Dim sw As StreamWriter = New StreamWriter(cs)
sw.Write(SourceStr)
sw.Flush()
cs.FlushFinalBlock()
ms.Flush()
Return Convert.ToBase64String(ms.GetBuffer(), 0, ms.Length)

End Function

'使用標準DES對稱解密
Public Function DecryptDes(ByVal SourceStr As String) As String

'get encodekey string from web.config
Dim sKey As String
sKey = ConfigurationSettings.AppSettings("EnCodeKey")

'put the input string into the byte array
Dim des As DESCryptoServiceProvider = New DESCryptoServiceProvider()

des.Key = ASCIIEncoding.ASCII.GetBytes(sKey)
des.IV = ASCIIEncoding.ASCII.GetBytes(sKey)

Dim buffer As Byte() = Convert.FromBase64String(SourceStr)

Dim ms As MemoryStream = New MemoryStream(buffer)
Dim cs As CryptoStream = New CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Read)
Dim sr As StreamReader = New StreamReader(cs)
Return sr.ReadToEnd()

End Function