Here is a new crypto idea - I would appreciate some feedback! Matt. My senior project is the extension of a grad student's *published* thesis entitled "Nonlinear CODEC in the digital domain". I use essentially a digitial filter to encode/decode the digital domain. I believe that it has applications to data security and I welcome people's input to this claim. The encoder. My prototype encodes 4-bits but I have software that works for n bits. If you would like to have the software let me know. I'm not an ASCII artist but here goes my best block diagram of the IIR digital filter encoder: x[n] ---------> + --------------------------> u[n] ^ | | | | | | | | -------------- | | z^(-1) | | -------------- | | | | | | + <------------------| ^ | | --------------- | | z^(-1) | | --------------- | | | | | --------------- | | Left Circ | | --------------- | | | | ---------------------- x[n] is the input data word, u[n] is the encoded output word, z^(-1) (z transform) is a delay element and Left_Circ is the left circulate function, i.e. Left_Circ(10)=5 (10 has binary representation 1010 and upon left circulation we get 0101 which has decimal representation 5). Another example is Left_Circ(3)=6. Clearly this filter is IIR with function: u[n] = x[n] + u[n-1] + Left_Circ( u[n-2] ) the decode is FIR and is found by solving for x[n] x[n] = u[n] - u[n-1] - Left_Circ( u[n-2] ) I won't bother you with another ASCII block diagram. I have run all kinds of signals (in software) through the filter pair. I get, what seems to me, a moderately secure coding of the digital domain with exact signal reconstruction from its coded form. Both Wavelet and Fourier techniques have failed to find anything "interesting" in the encoded domain. Please play around with this and send me feedback ( mlf3@Lehigh.EDU ) Matt. ________________________________________________________________ Matt Fante ________________________________________________________________