Methods and apparatus for implementing an n-state ripple-adder scheme coder with n≧2 using an n-state reversible switching function and a non-reversible n-state switching function acting upon a first and a second word of at least 2 n-state symbols are disclosed. Corresponding decoding methods and apparatus are also disclosed. A resulting codeword may be a codeword which can be decoded by using the identical or different n-state switching functions in a corresponding ripple adder scheme decoder. Feistel networks and LFSRs apply the coding and decoding. Systems using the coding and decoding methods may be communication, storage and/or financial systems.