Differential privacy framework still continue to be obscure in the following case:
If I make a set of queries, I can join their output to restore the original data. For this issue we have composition theorems that grants that every query consume just a "piece" of my $\epsilon$, so we can continue to answer queries for the total query "session" until I have pieces of my $\epsilon$.
So, my question is: what does "session" means? An attacker can make many sessions?
I think that is not very realistic that an user (that can be an attacker) can access just for a single "session" of queries (if we intend for "session" a "set of query that an user can make") . He could find a system to make "many sessions" (for example with different identities or similar, or working together with other attackers).
So, in these cases, how differential privacy works? Is there something that I misunderstand?