Got a crypto question here. Let's say I push out a list I'd like to keep secret to some client machine. The user of that machine must enter some ID or other piece of information. I want the client machine to perform a search of that ID vs the contents of a list (again, resident locally on that machine), but I don't want the user to be able to see the other entries of that list. Possible? Remember, after the initial push of data out to the client machine, no more messages are exchanged. This means the list must be sent in encrypted form. When the search is performed, the "stupid" thing to do (I think...someone correct me) is to take the user's ID, encrypt it, and then determine if matches an encypted member of the list (and I don't see encrypted each entry individually as a desirable thing). I am assuming that this allows a savvy user to reverse-engineer the encryption. Another option is one I don't have the background at this stage to understand. Let's assume the entire list has been encrypted in one shot. Is there some function such that when this encrypted list is convolved with the user ID a "Yes" or "no" can be obtained (indicating presence or absence from the list)? If the answer is yes, I'd also like to know if knowing this is farily basic to most encryption professionals sphere of knowledge... -TD _________________________________________________________________ Get McAfee virus scanning and cleaning of incoming attachments. Get Hotmail Extra Storage! http://join.msn.com/?PAGE=features/es