Systems and methods are provided for protecting and managing electronic data signals. In one embodiment a strong watermark is inserted in a data signal that is divided into a sequence of blocks, and a digital signature for each block is embedded in the signal via a watermark. The signal is then stored and distributed. When attempts are made to use or access the signal, the signal is checked for the presence of a watermark containing the digital signature for the desired portion of the signal. If the watermark is found, the digital signature is extracted and used to verify the authenticity of the desired portion of the signal. If not found, the signal is checked for the presence of the strong watermark, which if found causes the system to inhibit further use of the signal, and if not found further use of the signal is allowed.