Encrypt in 1.1 and Decrypt in 2.0

[Frank]

I need to send login info from a Windows application written in 1.1, and
from a classic asp web site, to a 2.0 web portal, where I need to
'auto-login' the clients.
Could you provide or point me to articles or guide me on how to:

1. Encrypt data in ASP.NET 1.1 and decrypt the same data sent in URL params
in ASP.NET 2.0

2 Encrypt data in classic ASP and decryptthe same data in URL params in
ASP.NET 2.0

Any help would be greatly appreciated,

Frank Kaesser