I am using xCode 4.3.1. After i created a project, i build it and tried to Archive. Then i got an error saying; (This is my first project in xCode 4.3.1)
The other issue here lies under Code Signing Identity under the Build Settings. Be sure that it contains the Code Signing Identity: "iOS Developer" as opposed to "Don't Code Sign." This will allow you to deploy it to your iOS device. Especially, if you have downloaded a GitHub example or something to this effect.
I had same problem with an Apple Sample Code. In project "PhotoPicker", in Architectures, the base SDK was:

This parametrization provokes the message:
CodeSign error: code signing is required for product type 'Application' in SDK 'iOS 7.1'
It assumes you have a developer user, so... use it and change:

And the error disappears.
I have same problem because option In-App Purchase was ON in project's Capabilities. If your app is not need in-app purchases - turn it off, or you need to set a correct provision profile to Debug scheme.
One possible solution which works for me:
Bravo!
This error was caused, for me, by different circumstances. A downloaded project tutorial had a default setting of [Project]>Targets>Build Settings>Architectures>Build Active Architecture Only>Release = "Yes." I wasn't intending to build a release, so the solution was to set Release (which presumably requires not just a developer profile but distribution profile) to "No."
You can get around this by using the simulator if you don't actually need to be deploying to a device. That solved it for me.