The file is too big to be stored on the blockchain, so it is stored on IPFS. Only the person who owns a unique Non Fungible Token (or a Security Token) can access it.
Of course I can encrypt the file in such a way that only the token owner can read it. However, when the owner sells the token, he must lose the access to it, and IPFS does not guarantee that the file will disappear from the network immediately.
Is it possible to implement such an access control?
Edit: Any tools are welcome if they allow to solve the problem, such as Zero Knowledge Proof protocols or other cryptographic (or non) tools which I 'm not aware of.