Abstract: An essentially pickproof padlock has a housing defining an interior chamber and a keyway with a stacked parallel arrangement of multiple annular cam rings fixed concentrically within the housing. The radially inward annular surface of each cam ring is formed with a respective raceway of a predetermined annular extent and disposition relative to the chamber. A tumbler assembly is disposed within the cam arrangement for selective relative rotational movement. The tumbler assembly has a plurality of slidable pins each with a head portion forming a bearing element. An associated key is formed with a plurality of parallel axial recesses for receiving the pins of the tumbler assembly, each recess being of a selected respective length terminating at a shoulder to collectively engage and move the head portions of the pins into respective operative dispositions within corresponding ones of the raceways wherein the tumbler assembly may be rotated by the key between locked and unlocked dispositions.