Encryption between F5 and .NET

We have a requirement to encrypt a cookie in a .NET 4 MVC website and that cookie then needs to be decrypted by an iRule. I have read that the F5 AES library is based on CWC cipher mode which doesn't appear to be supported in .NET. It looks like we should be using the F5 CRYPTO library instead of the F5 AES function calls. An example of code sharing encryption between .NET C and F5 would be extremely useful if that could be provided.