A non random salt isn't going to be very secure, in theory someone can generate every combo for your app (however thats unlikely).
I suggest you take a look RSA public key cryptography. You may want to have a look at How to use public encryption to manage licensing on android applications? .
Edit: I was a bit unclear on you question at first, Android: Do the random SALT bytes passed to AESObfuscator need to stay the same? i think is a duplicate that has an answer.