Mike Ingle sent out an inquiry in May about public-key encryption in WinFax 4.0 in Microsoft at Work. This is the reply which I received from someone here: We don't use D-H (Diffie Hellman is what I assume you were referring to) at all. We pick a 64 bit random number to RC4 with and send the number encrypted with an RSA key... I have made an inquiry specifically about WfW 3.11, but it may be a few days before I get a reply. Blanc