Lucca is using precomputed rainbow tables to attempt to crack hashed passwords from a data breach. He knows that two users have the same password, but the hashes do not match. What password hash security technique has Lucca most likely encountered?

Salting uses a unique, randomly generated string that is added to each password before it is hashed. That means that even matching passwords will not have the same hash. This prevents rainbow tables from being effectively used against password hashes due to the added computational load it creates for precomputing hashes.