How to have reliable developers and securing code from being stolen

I have couple of concept for website but they require immense coding and designing. For that I am planning to hire developers and designers [Contractors]. As I know this is going to take couple of months to complete I afraid that those developers (specially designers) can take away my code/design/concept. How can I protect my concept from being stealing by my own team?

Edit The reason why I am asking this question is because my friend had opened a Product based (software) development company and after 4 months few developers left the organization and developed the same product with that code. Eventually, due to financial crisis and wastage of 4 months my friend has shut down the company.

You can't, except by contract.

You are worrying about the wrong thing, thought. If your business plan contemplates hiring a couple of developers, letting them design your product and then firing them, you are in more trouble you realize. Just wait until the first bug appears after your original team is gone.

Edit: You seem to be worried because what happened to your friend. He having his source code "stolen" (he should start legal action, btw) is just part of the problem. If two products are identical, but only one is successful, what can be said of the failing company?

If you don't stop innovating, your competitors will have to follow you. You just need to become a leader.

And this is crucial: don't use contractors. Hire a killer team.

Take this for granted. There is almost nothing you can do to make your code/idea(s) 100% protected. That too only if you can catch them stealing your idea/code.

But allow me to propose a fail proof setup for you ;) :

1. Set up a few computers and secure/encrypt the hdds.
2. Make sure none the computers can connect to the internet but only to a local computer which can act as a code repository.
3. Disable all USB ports.
4. You can write a few scripts which will disable copy pasting if you are using Windows as your OS
5. Make your development team sign NDAs and come up with a very stringent policy.
6. Or Get a really big ass computer and create seperate VMs for all your developers. Make them connect to the VM and ask them to develop their code on the VM. of course take precautions for data transfer.

This will make sure that this is the slowest form of software development. What will you do if they can remember the code and go home and make this own up ? Most coders will take some code home to build their own libraries which help them with their day to day job, some will take it home to resell it. There is really nothing you can do. I dont know which country you are from. But you have to know your local situation and then take a call whether a contract can really be enforced or not. So this is a gamble you have to take. Or if you are technical enough, just make the entire thing on your own, which may take some time but hey no one aint stealing nothing.

HTH