Accessing .asp cookie from ASP.net

ksams · July 5th, 2004, 04:53 AM

I have encrypted and storing a string in cookie in .asp page. When I access this .asp cookie and decrypt it back in ASP.net page, I am not getting the original string. But if I I access this .asp cookie and decrypt it back in a .asp page, I am getting the original string, what is it so?

Thanks and Regards

bmains · July 5th, 2004, 08:52 AM

Hello,

If you are getting a different string, can you verify that the algorithms are the same? They probably are using a slighly different algorithm. If you can't get that to work, I would consider using a component to do the encrypt/decrypt. That way, both ASP and ASP.NET could use the same component.

Brian

planoie · July 5th, 2004, 09:54 PM

Can you confirm that you are actually getting the cookie value back, apart from the encryption/decryption?

ksams · July 7th, 2004, 01:10 AM

When i am retrieving the encrypted value stored in a ASP cookie in a ASP.net page using HTTPCookie, i am getting a different encrypted value in ASP.net compared to the encrypted value stored in a ASP cookie in a ASP page.

does not the HttpCookie in ASP.net store the special characters?? Is it so?

Imar · July 7th, 2004, 02:34 AM

Hi there,

I ran into this issue a long time ago as well. Here's how I fixed it.

In classic ASP, set cookies like this:

Code:

  Response.Cookies("MYNetCookie") = ConvertCharsToEntities ("YourValue")

  Function ConvertCharsToEntities(s)
    Dim i, c
    For i = 0 To (len(s) -1)
      If i > 0 Then
        c = c & "-"
      End If 
      c = c & (Asc(Mid(s, i+1, 1)))
    Next
    ConvertCharsToEntities = c
  End Function

Then in .NET you can get the cookies value like this:

Code:

  MyCookieString = UrlDecode(Request.Cookies("MYNetCookie").Value.ToString())

Code:

  ' Split to array with all asc codes
  arrMyValue = Split(MyCookieString, "-")

  Dim i As Integer = 0
  For i = 0 To ((arrMyValue.Length) - 1)
      MyCookieValue &= Chr(arrMyValue(i))
  Next

  ' At this point, MyCookieValue should contain the initial string

Basically what this does is convert each character in your original string to its associated numeric value. Then this long string of numbers (separated by a dash) is stored as the cookie's value.
In .NET the reversed process takes place: The cookie value is split on the dash, and each number is used to retrieve its associated string value to return the original string.

I can't really recall what the problem was, but I can imagine it has something to do with the way the cookie is sent as plain text or unicode. With "normal", low ascii values there is usually not a problem, but encrypted strings often contain a lot of weird characters.

This code is over 3 years old, so it may fix a problem that no longer exists in .NET 1.1 or 1.0 with a service pack. But it's worth a try.....

Hope this helps, and if it does, can you let me know?

Imar
---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.
While typing this post, I was listening to: Hyper chondriac music by Muse (Track 10 from the album: Hullabaloo) What's This?