For clarity, let's assume the hospital stores its records in plaintext. For the pharma company, the hospital encrypts the patient records with a secret key. Now

For clarity, let's assume the hospital stores its records in plaintext. For the pharma company, the hospital encrypts the patient records with a secret key. Now they let the pharma company run their homomorphic algorithm and send the values back. Only problem is the pharma company can not read those results without having access to the key. FHE is completely redundant in this use case - the hospital could have simply run the pharma company's SQL and audited the code and outputs. What is FHE actually good for then? Let's imagine you are a top secret agent and you get instructions to fly to Bulgaria as a part of your mission. You have other hostile agents constantly monitoring you, trying to understand your next move. But there's a problem - to buy a plane ticket to Bulgaria you need to know the name of its capital city. You can't just type it to Google, because these other agents have actually infiltrated the Google servers and can see everything you search (assume once you actually know the name of the capital, you can somehow buy the actual ticket without "them" knowing..) Lukcily though, CloudCorp offers a public homomorphic query service for all world capitals. This service allows you to send a query for the capital of any country over an intercepted connection, and get back the result. Even if the hostile agents had infiltrated CloudCorp and were monitoring all your comms, they would not be able know which country's capital you just queried. Not even CloudCorp could do that, you are the only person who knows what you asked and what was the result. How such service would be implemented is explained in good detail in this tutorial, completele with working code: https://github.com/homenc/HElib/tree/master/examples/BGV_country_db_lookup https://github.com/homenc/HElib/tree/master/examples/BGV_cou... P.S. The capital of Bulgaria is Sofia.