Reading/Decrypting ASP.Net auth cookie from ASP

[OTS]

I have mixed ASP & ASP.Net sites. I want to read an encrypted
FormsAuthenticationTicket from an ASP page (I already have multiple ASP.Net
apps reading the tickets).

Given the information from the <machineKey> section of web.config, what are
the steps to decrypt the cookie? I would like to access the userinfo data in
the ticket.

I have a C++ component that grabs the cookie, the question is whether to do
the decryption there or somehow call into a managed library and use the
managed decryption (if I can get the proper machineKey context loaded).

Thanks in advance