A lock assembly incorporating a number of features designed to defeat attempts to pick or destroy the lock. The lock cylinder assembly employs multiple arrays of pass key pins, making picking of the lock much more difficult. Second, the arrangement of the pass key pins in separate arrays requires that multiple cuts would have to be made into the lock housing mogul or cylinder blank in order to defeat the lock cylinder assembly. Third, the lock cylinder assembly of the present invention may incorporate multiple sets of hardened dowel pins to prevent drilling through the lock housing mogul in the area of the driver pins. Fourth, the lock cylinder assembly of the present invention may incorporate a hardened cylinder shield behind the front face of the cylinder blank to prevent drilling through the cylinder blank.