Codestream Length-Invariant Partial Scrambler Using DCT Signs for Motion JPEG Movies

This paper proposes a partial scrambling method for motion JPEG movies that inverts bits representing the positive and negative sign of particular AC coefficients in a codestream to scramble the codestream. Utilizing the relation between motion and the positive and negative sign of coefficients, moving object detection is not required in this method. Moreover, the proposed method completely descrambles codestreams to the original by simple inversion of bits without any knowledge on the position and shape of moving objects. The codestream domain processing in this method serves low processing time and invariant coding efficiency. Simulation results show the effectiveness of the proposed method