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Encrypt Querystring using CAPICOM?

Posted on 2006-07-13
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Last Modified: 2012-06-27
In ASP is it recommended to use CAPICOM (CAPICOM.EncryptedData) to encrypt the URL Querystring?  
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Question by:thespiceman
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by:alorentz
ID: 17101581
What's the point?  Why do you need to encrypt?
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by:jitganguly
ID: 17101831
If you really want to encrypt use POST method. These days hackers can break anything with the URL. POST is very secured and it only breaks when they hack the whole website.
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Author Comment

by:thespiceman
ID: 17101853
I recently encrypted the querystring using the Vernam Encryption technique http://www.4guysfromrolla.com/webtech/012000-1.shtml.  This was done to prevent altering parameters in the querystring which was allowing the user to view products that were not yet released to the public. Works great...BUT...my manager wants to replace the Encrypt() and Decrypt() functions with the following ones that we use for encrypting data stored in our cookies.  I need to know if this is as secure as the Encrypt() and Decrypt() functions and methodolgy described in http://www.4guysfromrolla.com/webtech/012000-1.shtml?

function Encrypt(val)
      On Error resume next
      err.Clear
      set message = server.CreateObject("CAPICOM.EncryptedData")
      message.Content = val
      message.SetSecret MSCSSite.DisplayName

      message.Algorithm.Name = 1 'CAPICOM_ENCRYPTION_ALGORITHM_RC4

      'Encrypt the message storing the result in the encryptedmessage string
      Encrypt = message.Encrypt
      
      if err.number <> 0 then
            Encrypt = val
      end if

      ' Release the EncryptedData object.
      Set message = Nothing

end function

function Decrypt(val)
      On Error resume next
      err.Clear
      set message = server.CreateObject("CAPICOM.EncryptedData")

      ' If a message was read in (the length of the input string is
      ' greater than 0), set the password and decrypt the message.
      If Len(val) > 0 Then
            message.SetSecret MSCSSite.DisplayName
          message.Decrypt val
          Decrypt = message.Content         
            if err.number <> 0 then
                  Decrypt = val & "_ERR"
            end if
      Else
            Decrypt = val
      End If

      Set message = Nothing
end function
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by:jitganguly
ID: 17101932
Well what kind of encryption technology is used in CAPICOM ? Is that better than the one you currenlty use ? Go though their technical review.
But all these 3rd part tools are better than standard encrytion through VBScript. Iuse this simple VBScript stuff, but I am sure these guys use much better than this

Function P2E(myPass)
Dim i

    P2E = ""
    For i = 1 To Len(myPass)
        P2E = P2E & Chr(Asc(Mid(myPass, i, 1)) + i)
    Next

End Function


Function E2P(myPass)
Dim i

    E2P = ""
    For i = 1 To Len(myPass)
        If Asc(Mid(myPass, i, 1)) > 32 Then
           'Response.Write Mid(myPass, i, 1) & " - " & chr(Asc(Mid(myPass, i, 1))-i+1)& "<br>"
           E2P = E2P & Chr(Asc(Mid(myPass, i, 1)) - i)
        End If
   Next
End Function
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Expert Comment

by:CyrexCore2k
ID: 17103380
"If you really want to encrypt use POST method. These days hackers can break anything with the URL. POST is very secured and it only breaks when they hack the whole website."

Um, that's completely incorrect. I'm not trying to be rude or anything but hackers can break anything using the POST method just as easily as a query string.
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Expert Comment

by:CyrexCore2k
ID: 17103506
Using a packet sniffer it would take about the same amount of time. Look the point is that your statement "POST is very secured" is not only wrong but dangerously misleading. Normally I don't say anything when experts make mistakes but I felt that telling someone that POST is somehow secure could lead someone to design a site with deadly security flaws.
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Assisted Solution

by:CyrexCore2k
CyrexCore2k earned 350 total points
ID: 17105390
thespice - Sorry to get of track.

Since I don't know exactly how CAPICOM encrypts strings I can't say for sure. But personally I would trust it. It's not a very complicated encryption task and if it's been working for your cookies it should work fine for your query strings. If you really want to know for sure I would do away with CAPICOM altogether and encrypt is using an RC4 algorithm since 1) it's industry standard  2) you can see the source code and best of all 3) it's free.
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Accepted Solution

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kevp75 earned 150 total points
ID: 17105407
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Expert Comment

by:SimonBlake
ID: 17107465
thespice - I've done some work with RC4 and encryption before - one of the holes you might fall foul of is the MS implementation of URL encoding (This issue is also present on Oracle's web server as well) in that null bytes (hex 00) don't get encoded correctly, so when you try to decode at the other end it gives a different result.

My advise to you is to use a custom url encoder ontop of the encryption at both ends regardless of form or query string data otherwise you will be scratching your head for hours!

S.
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