Ruling on using the returns on investment certificates for postgraduate education
Question

Is it permissible to use the returns on investment certificates that my father did for me to pay for my education, especially postgraduate studies such as a master’s degree?
Praise be to Allah.All kinds of investment certificates issued by riba-based banks are haram, as we have explained in fatwa no. 98152 . 
Based on that, the returns that come from dealing in these certificates that your father made in your name, are haram, and it is not permissible for the owner to make use of them in paying any of his expenses. 
What you have mentioned about postgraduate education is one of your expenses, so your father does not have the right to spend on you for that purpose from haram wealth, and you do not have the right either, if the certificates are your name, to make use of the haram returns. 
If they are not in your name, then you should not take anything for your expenses from haram wealth, even if your father is giving it to you. Rather what you should do is rid yourself of these returns by giving them to charitable causes or spending them in the public interest, as we have explained in fatwa no. 128641
What you must do now is encourage your father to repent from these haram transactions, and get rid of the riba-based contracts and dealings, because riba is one of the gravest and worst of major sins. Allah, may He be exalted, says (interpretation of the meaning):
“O you who believe! Fear Allah and give up what remains (due to you) from Ribaa (from now onward) if you are (really) believers.
279. And if you do not do it, then take a notice of war from Allah and His Messenger but if you repent, you shall have your capital sums. Deal not unjustly (by asking more than your capital sums), and you shall not be dealt with unjustly (by receiving less than your capital sums)” [Al-Baqarah 2:278-279]. 
And Allah knows best.