2. The method of claim 1 , further comprising generating the hash value, the generating of the hash value comprising: dividing the unidentified information signal into frames; computing a hash word for each frame; and concatenating successive hash words to constitute the hash value.
3. The method of claim 2 , wherein the computing of a hash word for each frame includes: dividing each frame of the information signal into one of bands or blocks; calculating a property of the signal in each of said bands or blocks; comparing the properties in the bands or blocks with respective thresholds; and generating respective bits of the hash word based on the results of said comparisons.