A mechanical cipher lock comprising an anti lock-breaking plate 1 on which a notch 11 is defined corresponding to each cipher key 2, wherein each cipher key 2 has a projection 21 in its lower part, and wherein the notch 11 is configured for achieving a grip with the projection 21 so as to prevent the cipher key 2 moving longitudinally, e.g. up/ down. The grip may be achieved through the turn of a knob 3. The plate 1 may be a flat panel, in the middle of which a rectangular through-hole is defined for the cipher keys 2 to penetrate. Preferably, the notches 11 are configured in intervals along the two long sides of the rectangular through-hole. The invention improves lock security by preventing hand sensing, i.e. the exploitation of assembling clearance or diastema in the lockset to find the code by comparing feel or pressing force per cipher button.
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