An interesting idea, although highly unpracticable. Sending a binary is nearly impossible. As an example, I have at my disposal (and I log into regularly) at least 6 different platforms. All Unix, but each one would require its own binary! This doesn't mean that your idea has no merit. On the other hand, it is an interesting key distribution model. Except there are a number of problems that I can see. First, anything you know about the person is something that someone else could probably do a little research and find out as well. This inherently means it is not a very secure channel, rather it is only moderately secure. Also, there is no way to meet your goal of "no external binary needed." There may be a few things you can do in lieu of this, but all of them require some knowledge of the recipient hardware system. But in a case such as mine, even that wouldn't help (do you send it for an RT, Vax, Decmips, RS6000, Alpha, Linux, Sun386i, Next, ...?) Like I said, its an interesting key distribution model, but I do not see any way to realize it under your assumptions. -derek