The present invention relates generally to computer software, and more specifically, to a method and system of making computer software resistant to tampering and reverse-engineering. Tampering refers to changing computer software in a manner that is against the wishes of the original author, and is distinct from obscurity techniques which do not change the underlieing data or control flow of a program. Broadly speaking, the method of the invention is to analyse the effectiveness of various encoding techniques by measuring the number of possible decodings corresponding to a given encoded world. This analysis gave rise to a number of new data flow encoding techniques including alternative mixed encoding (a combination of linear and residue number encoding), and multinomial encoding.