I can't code sign my iOS application

Question

I've purchased the developer program earlier and I've installed the certificate into my keychain (both iPhone developer and iPhone distribution). When I'm going to deploy apps to real devices, Xcode gives me this error:
Code Sign error: There are no valid certificate/private key pairs in the default keychain.
When I go to Organizer>Teams, there is an error and here is the message:
Unable to code sign using identities in this team: no private keys available.
And when I go to Provisioning Profiles, there is this error: Valid signing identity not found.
I've tried downloading the certificates from the portal and move them to my keychain again, but I've seen that no keys are coming with these certificates. Where can I get the keys? And also, I didn't see the Software Signing certificate in my keychain either. How can I solve this problem?

Solution

I've resolved this problem by deleting everything related to signing of apps (so in Xcode, Keychain Access, and on developer.apple.com) and make new profiles following the wizard (called launch assistant) on the homepage of the provisioning portal.