对称加密解密模块

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本文介绍了一个使用DES算法实现的对称加密解密模块。该模块通过VB.NET编程语言实现，能够将明文转换为密文，并能将密文还原为原始明文。加密过程涉及字符串转换、密钥生成及加密流操作。

Imports System.Text

Imports System.Security.Cryptography

Module ModSecurity

Function EnText(ByVal Text As String, ByVal sKey As String) As String

Text = Text.ToLower

Dim des As New DESCryptoServiceProvider

Dim inputByteArray() As Byte

inputByteArray = Encoding.Default.GetBytes(Text)

des.Key = ASCIIEncoding.ASCII.GetBytes(Left(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5"), 8))

des.IV = ASCIIEncoding.ASCII.GetBytes(Left(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5"), 8))

Dim ms As New System.IO.MemoryStream

Dim cs As New CryptoStream(ms, des.CreateEncryptor, CryptoStreamMode.Write)

cs.Write(inputByteArray, 0, inputByteArray.Length)

cs.FlushFinalBlock()

Dim ret As New StringBuilder

Dim b As Byte

For Each b In ms.ToArray()

ret.AppendFormat("{0:X2}", b)

Return ret.ToString()

End Function

Function DeText(ByVal Text As String, ByVal sKey As String) As String

Dim des As New DESCryptoServiceProvider

Dim len As Integer

len = Text.Length / 2 - 1

Dim inputByteArray(len) As Byte

Dim x, i As Integer

For x = 0 To len

i = Convert.ToInt32(Text.Substring(x * 2, 2), 16)

inputByteArray(x) = CType(i, Byte)

des.Key = ASCIIEncoding.ASCII.GetBytes(Left(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5"), 8))

des.IV = ASCIIEncoding.ASCII.GetBytes(Left(System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5"), 8))

Dim ms As New System.IO.MemoryStream

Dim cs As New CryptoStream(ms, des.CreateDecryptor, CryptoStreamMode.Write)

cs.Write(inputByteArray, 0, inputByteArray.Length)

cs.FlushFinalBlock()

Return Encoding.Default.GetString(ms.ToArray)

End Function

End Module