To run that scenario, Hcp B scans the delegations of patient 1234 and notices that Hcp A has shared a primary key with him. He either reuse the hcp key that he saved from a previous operation or recovers it, decrypts it and saves it for later use. Using the decrypted hcp key {AB}, he decrypts the encrypted primary key. Using ABCD, he can now query the database and obtain the connected contacts.