You can reduce this workload by using an asymmetric algorithm like RSA to store an intermediate key. Post = P Symmetric encryption of X with key Y = E(X, Y) P

You can reduce this workload by using an asymmetric algorithm like RSA to store an intermediate key. Post = P Symmetric encryption of X with key Y = E(X, Y) Posts are stored as E(P, K_master) Authorizations to posts are stored as E(K_master, K_reader) You can trust your friends (that don't own quantum computers) with your RSA public key, allowing them to E(K_master, K_you) data that can only be decrypted with your private key. It is weak to a known plaintext attack (in which a user Eve with both K_master and E(K_master, K_alice) could attack Alice's private key), and of course weak to an authorized user sharing the master key. It's also weak to copy and paste, just like every other private social network.