1. An apparatus for generating a signature of an input signal comprising: a plurality of computational cores coupled to the input signal, each core having properties that have at least some statistical independency from other of said computational cores, said properties being set independently of each other core, each generate responsive to the input signal a first signature element and a second signature element, said first signature element being a robust signature; wherein a plurality of said first signature elements comprise a first signature of the input signal and a plurality of said second signature elements comprise a second signature of the input signal, said first signature determined respective of a first threshold value which is higher than a second threshold used to determine said first threshold value, said first signature being robust to at least one of noise and distortion.