Linear Feedback Shift Register - Science topic

LFSRs are not secure, so if you plan to use them as is in a block cipher don't. If you plan to use them as a defusion layer then ok but it doesn't add more security.

Two related transforms on a Boolean function f of order n are used: the Fourier-Hadamard (FH) and Walsh (W). FH linearly maps f to the real valued function \hat{f}(u)= \sum_{x\in\mathbb{F}_2^n}(-1)^{f(x)\oplus u . x} where u.x is the inner product. When applied to the sign function f_\chi (x)=(-1)^f(x), FH corresponds to W. Details can be found in C. Carlet. Boolean Functions for cryptography and error-correcting codes. Technical report, University of Paris 8, 2011