Encryption

[Guddu]

hi

i am passing clientid through querystring.now what i want to do is to encrypt this id.

my url is like this

https://www.shail.com/Portal/admin/clientadmin/employeeSummary/frameset.asp?lngClientID=1202&strPage=Summary

any good way for encryption?
thanx

[barneybabe]

I use the following simple encryption method

<%
	//---This is to encrypt and decrypt
   Dim sbox(255)
   Dim key(255)

   Sub RC4Initialize(strPwd)
   '----  This routine called by EnDeCrypt function. Initializes the   sbox and the key array)                                   

      dim tempSwap
      dim a
      dim b

      intLength = len(strPwd)
      For a = 0 To 255
         key(a) = asc(mid(strpwd, (a mod intLength)+1, 1))
         sbox(a) = a
      next

      b = 0
      For a = 0 To 255
         b = (b + sbox(a) + key(a)) Mod 256
         tempSwap = sbox(a)
         sbox(a) = sbox(b)
         sbox(b) = tempSwap
      Next
   
   End Sub
   
   Function EnDeCrypt(plaintxt, psw)
   '--  This routine does all the work. Call it both to ENcrypt   and to DEcrypt your data.                                  
      dim temp
      dim a
      dim i
      dim j
      dim k
      dim cipherby
      dim cipher

      i = 0
      j = 0

      RC4Initialize psw

      For a = 1 To Len(plaintxt)
         i = (i + 1) Mod 256
         j = (j + sbox(i)) Mod 256
         temp = sbox(i)
         sbox(i) = sbox(j)
         sbox(j) = temp
   
         k = sbox((sbox(i) + sbox(j)) Mod 256)

         cipherby = Asc(Mid(plaintxt, a, 1)) Xor k
         cipher = cipher & Chr(cipherby)
      Next

      EnDeCrypt = cipher

   End Function

//================Usage

//---this can be any text but use the same text to encrypt and decrypt
psw = "anytext"
//---To encrypt
Enc = EnDeCrypt("hello" , psw) 
response.write Enc &"<br>"
//---to decrypt
Dec= EnDeCrypt(Enc , psw) 
response.write Dec &"<br>"
%>

Important note:- when you pass the encrypted value as querystring you have to use Server.URLEncode(encrptedvalue) otherwise it will not be correctly decrypted.

[Guddu]

thanx for reply let me check

[Guddu]

hi i m getting divide by zero error at this line

 key(a) = asc(mid(strpwd, (a mod intLength)+1, 1))

[barneybabe]

what is the pwd and the string you are trying to encrypt?

[Guddu]

now its working...i m not using server.urlencode but still working

[barneybabe]

It would be better you use the server.urlencode otherwise you may get into trouble later.

[Guddu]

okay thanx a lot