Multi-level watermarking with independent decoding

A drawback of most watermarking techniques is the need for some additional information in order to retrieve the watermark. Additionally, the robustness of the watermark decreases as the number of information bits stored in the image increases. We present a watermarking technique which requires no information for decoding in addition to the watermarked image. The watermark is multi-level with few bits embedded robustly at low levels and longer watermark sequences embedded less robustly at higher levels. This allows detection of "tampered" and "attacked" images by detection of existence of the watermark at low levels and deterioration of the watermark at high levels. In order to prevent interference of the watermarks at different levels various image representation spaces are used. The watermark is shown to be non-visible and robust