如何给 URL地址栏中的参数加密、解密？

加密写法URLEncode(str)

<%
Function URLDecode(enStr) 'URL解碼函數
dim deStr
dim c,i,v
deStr=""
for i=1 to len(enStr)
c=Mid(enStr,i,1)
if c="%" then
v=eval("&h"+Mid(enStr,i+1,2))
if v<128 then
deStr=deStr&chr(v)
i=i+2
else
if isvalidhex(mid(enstr,i,3)) then
if isvalidhex(mid(enstr,i+3,3)) then
v=eval("&h"+Mid(enStr,i+1,2)+Mid(enStr,i+4,2))
deStr=deStr&chr(v)
i=i+5
else
v=eval("&h"+Mid(enStr,i+1,2)+cstr(hex(asc(Mid(enStr,i+3,1)))))
deStr=deStr&chr(v)
i=i+3
end if
else
destr=destr&c
end if
end if
else
if c="+" then
deStr=deStr&" "
else
deStr=deStr&c
end if
end if
next
URLDecode=deStr
end function

function isvalidhex(str)
isvalidhex=true
str=ucase(str)
if len(str)<>3 then isvalidhex=false:exit function
if left(str,1)<>"%" then isvalidhex=false:exit function
c=mid(str,2,1)
if not (((c>="0") and (c<="9")) or ((c>="A") and (c<="Z"))) then isvalidhex=false:exit function
c=mid(str,3,1)
if not (((c>="0") and (c<="9")) or ((c>="A") and (c<="Z"))) then isvalidhex=false:exit function
end function
%>