Change password daily based on a key

I want to add the ability to my program that when it starts up an engineer has to enter a password.

I was thinking that each engineer is give their own key and based on this key and a daily changing public key it will allow them access to the program.

The reason I am thinking this way is because there is a program that they might leave at a customer's site which needs to be protected. If something is changing daily then the customer will not be able to access it even if they know a key on one day.

If there is some other approach I'm open to it thanks.

UPDATE: This program is a licence generator which enables/disables features for our main program . Obviously if this gets left on si开发者_如何学运维te then we lose money possibly.

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You could use a 2-factor key fob like this: http://www.rsa.com/node.aspx?id=1156

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Why don't you just distribute the program on an USB stick and run from there or for some reason not possible? It would save you the trouble of thinking of a password, the usb stick contents code be encrypted so even if it is lost you are safe.

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What 'we' do is that we have a daily changing key that needs to be entered into the support program. Though the program can be left anywhere, engineers simply have access (for example on an USB stick) to generate these one-day keys. Variations on this are available.

These key generator tools can of course be keyed to individual personel.