Abstract: A ball spline having reinforcement bush parts includes a spline shaft having concave track grooves formed to extend along the longitudinal direction thereof; a nut part in which the spline shaft is inserted and movable along the longitudinal direction thereof; and a plurality of balls provided between the nut part and the spline shaft to circulate, wherein: the nut part includes a nut which is a hollow body where the spline shaft is inserted, and retainers which are hollow bodies which are provided at longitudinally opposite sides of the nut and into which the spline shaft is inserted; two spline parts and two reinforcement bush parts are provided at the nut part; some of the balls circulate and move between a track groove and a load track groove and along a no-load circulation part; and the remainder of the balls roll circulate and move along the reinforcement bush parts.

Abstract: An apparatus for encrypting an image frame generates a key frame, performs XOR with the image frame and the key frame to generate a temporary image frame, and changes positions of blocks of the temporary image frame according to a first key to generate an encrypted image frame. An apparatus for decrypting an image frame receives an encrypted image frame, generates a key frame, changes positions of blocks of the encrypted image frame according to a first key to generate a temporary image frame, and performs XOR with the temporary image frame and the key frame to generate the image frame.