ITunes iPhone backup passowrd
I am attempting to backup my iPhone via iTunes. Under the 'Backups' page the prompt for 'Encrypt iPhone backup' is already checked. When I try to uncheck it I am asked for a password to unlock it. If I click on 'Change password' I am asked for a password to change it.
I never entered a password in iTunes so how do I know what password to use? I have tried my iPhone passcode and my Apple id password - nothing works.
How do I get by this step?
On another topic I want to backup and then restore my phone because all my photos have disappeared. I know they are still on the phone because they are taking up storage space so I'm hoping I can see them again if I restore a backup.
iPhone 6, iOS 10.2.1