Data Security, Encryption

[Tom at SDI]

I'm developing a WebService using C#. I've got a client app that is
non-dot-net. I intend on placing the web service on https, but some data is
sensitive and our clients may expect more data security. I am currently
looking at data encryption using System.Security.Cryptography on the .NET
side and the CryptoAPI on the client side, but am having some difficulty
there.

Is there any data encryption mechanism built into web services themselves
that I can make use of, thus bypassing the need to use the CryptoAPI?

Thanks,

Tom