1. A method for protecting a digital signal, comprising: obtaining a digital signal comprising a plurality of digital blocks; transforming, using a processor, each of the digital blocks into the frequency domain using a spectral transform; identifying a plurality of frequencies and associated amplitudes for each set of the transformed digital blocks; selecting a subset of the identified amplitudes based on the survivability of message information against signal manipulation; choosing said subset of the identified amplitudes for each of the digital blocks using a primary mask from a key; choosing message information using a transformation table generated with a convolution mask; and, encoding, using a processor, the chosen message information into said transformed digital blocks by altering the selected amplitudes based on the chosen message information.