I will demonstrate my question with an example.
I want to develop a distributed application for renting cars. Since the booking details (BD) can be visible on the blockchain, I want to encrypt them and be accesible only by the intended users. Assume that the car owner and the renter have public key and private key, the car has a key (symmetric encryption) and that the onwer and the renter have agreed beforehand on the BD.
The idea is that the owner will generate an access token, from the BD, which will be published on the blockchain, retrieved by the renter and used by him to enter the car.
My question is how can I encrypt the BD in order to generate the access token while at the same time confidentiality, integrity and availability can be maintained.
One ill-solution that I have thought is that the owner encrypts the BD and their signature with the car's key (in order to generate the access token). Then he publishes the access token to the blockchain and retrieved by the renter. However, how can the renter know that the access token contains the agreed BD? Is it good practice to use a second layer of encryption such that; after the owner generates the access token he encrypts it together with the BD with the renter's public key? In this scenario, when the renter decrypts it, he has two things, an access token (which will be used to enter the car) and the booking details (verify that these are the agreed BD).
Is there a more efficient or elegant way to do this?
Thank you in advance.