My latest article was just published in the June '03 edition of MSDN Magazine.  You can read it online at http://msdn.microsoft.com/msdnmag/issues/03/06/NETRemoting/default.aspx.

Summary: "As .NET Remoting gains popularity in the enterprise space, it must meet business demands for trustworthy computing. Remoting traffic can be secured when objects are hosted in IIS, but when they aren't hosted in IIS, custom security solutions can be developed. This article provides an in-depth look at writing channel sinks for .NET.  It details the flow of data through custom channel sinks and explains the kinds of manipulations that can be performed on that data."

An example pair of sinks is detailed (with code available for download) that demonstrates how asymmetric encryption could be implemented for remoting.  Please note that it is only a sample implementation used to show various ways remoting can be extended, not as a production-ready solution.