1. An information insertion/detection system for detecting and inserting DCT coefficients in image signals, comprising: a resolution analyzer for receiving image code data and outputting the image code data and information of size of an image of the image code data; an insertion pattern determining unit for receiving the image code data and the image size information and outputting the image code data and pattern information; an information inserter for receiving the image code data and the pattern information and producing image code data by inserting information of the DCT coefficients into the image code data; and a video analyzer for receiving the image code data and producing information of insertion strength of the DCT coefficients.