Signal processing is fun, and its principals crop up in unexpected ways. Grokking convolutions and auto-corelations is a nice "bump" in the way I think about data processing. Seeing data as a stream instead of discrete chunks sometimes helps a simple convolution be apparent when facing a naive implementation's taxing computation. What this would have to do with security, I don't know.

I think that tptacek's point is that he wants someone that "digs deeper".