Q: When you're about to restore your device from an iTunes backup, a small window pops up and says: "Write your password to unlock your iPhone-backup". The thing is I've never made or heard about this "backup code" so I don't know what I should or can do?

This window "Write your password to unlock your iPhone-backup" keeps popping up on my screen and prevents me to restore my phone. I'm trying to restore my new iPhone 5s with my old iPhone's back up from iTunes (which I made yesterday) and I'm unable to do so, because of this backup code that i've never heard of until now and never made one.  So I have no idea what I should do? I've tried to redo my backup from iTunes but again do I have to use this code, which I never made, but my Mac Book keeps telling me to write it. Have anybody tried or is familiar with this situation I'm in ? If so I would really appreciate if you could help!