I was trying to restore a backup from my computer to my iphone , however it's set to be password protected. I do not know the password, as I've never set one. I've tried all the passwords I know, which I've ever used to make sure I didn't set it. Nothing worked. any advises
If you never set one, it then should be the passcode you used to unlock your phone (the 4-6 digit PIN) when you performed the back up.
If that doesn't work, look in your Keychain Access app, in your Utilities folder. Launch it, search for "iphone backup", and chances are you'll get a match. Open the item, click "show password" and enter your Mac system password.