This assembly includes a security apparatus equipping a lifting device, in particular a winch, and a system for actuating the apparatus The security apparatus includes a toothed wheel, wedged on the shaft of the lifting device, and a worm meshing with the toothed wheel. The assembly also includes: a splined shaft secured to one end of the worm; a pocketed wheel with inner and outer splines, engaged on the splined shaft; an elastic member between the pocketed wheel and a stop piece; a drive wheel with a splined hub, with which the pocketed wheel is capable of engaging rotationally; and a back-up motor, capable of rotating the drive wheel.