The main idea is that randomly select two disjoint subsets of equal size out of instruction set and this selection is the watermark which is superimposed by changing the elements of one subset by adding a positive integer factor 在程序的指令集中随机抽取两个不相交的基数相等的子集，对特定子集的选取就是要嵌入的水印。改变程序使对应于某个子集的所有指令的出现次数都增加一个常数。
