Is it permissible to eat from a medical conference buffet for which only the father's subscription was paid?

If every guest pays for themselves at the conference, then you or your father must pay your subscription fee. If this is not done, or permission is not obtained from the restaurant owner, then it is forbidden to eat their food without their permission, based on the hadith: "Indeed, your blood, your wealth, and your honor are sacred to you." It is permissible for your father to share with you the portion of food and other items allotted to him.