I'm using XOR encryption in my Samsung smart TV Web application which is use a static secret key for encryption and decryption.
So, what is the best way to store secret?
There is a Web API which could be used for secure storing application data - tizen.keymanager.saveData. You can use it for storing some string data and protect this with password - it seems to fit your needs.
Additional feature is that you can share access to this value between several applications, by setting permission.