使用ASP加密算法加密你的数据（二）

在第一部分，讨论了如何生成密钥，下面将介绍如何使用这个密钥来加密和解密一个字符串。
　　下面的代码就是能够同时实现这个功能的函数
Crypt.asp文件
<%
Dim g_Key
Const g_CryptThis = "Now is the time for
all good men to come to the aid of their country."
Const g_KeyLocation = "c:key.txt"
g_Key = mid(ReadKeyFromFile(g_KeyLocation),1,Len(g_CryptThis))
Response.Write "

ORIGINAL STRING: " & g_CryptThis & "

"
Response.Write "

KEY VALUE: " & g_Key & "

"
Response.Write "

ENCRYPTED CYPHERTEXT: " & EnCrypt(g_CryptThis) & "

"
Response.Write "

DECRYPTED CYPHERTEXT: " & DeCrypt(EnCrypt(g_CryptThis)) & "

"
Function EnCrypt(strCryptThis)
Dim strChar, iKeyChar, iStringChar, I
for I = 1 to Len(strCryptThis)
iKeyChar = Asc(mid(g_Key,I,1))
iStringChar = Asc(mid(strCryptThis,I,1))
' *** uncomment below to encrypt with addition,
' iCryptChar = iStringChar + iKeyChar
iCryptChar = iKeyChar Xor iStringChar
strEncrypted = strEncrypted & Chr(iCryptChar)
next
EnCrypt = strEncrypted
End Function
Function DeCrypt(strEncrypted)
Dim strChar, iKeyChar, iStringChar, I
for I = 1 to Len(strEncrypted)
iKeyChar = (Asc(mid(g_Key,I,1)))
iStringChar = Asc(mid(strEncrypted,I,1))
' *** uncomment below to decrypt with subtraction
' iDeCryptChar = iStringChar - iKeyChar
iDeCryptChar = iKeyChar Xor iStringChar
strDecrypted = strDecrypted & Chr(iDeCryptChar)
next
DeCrypt = strDecrypted
End Function
Function ReadKeyFromFile(strFileName)
Dim keyFile, fso, f
set fso = Server.CreateObject("Scripting.FileSystemObject")
set f = fso.GetFile(strFileName)
set ts = f.OpenAsTextStream(1, -2)