Methods and systems for verifying a hardware design for an integrated circuit that implements a function that is polynomial of degree k in a sub-function p over a set of values of p, k being an integer greater than or equal to one. The methods include: verifying that an instantiation of the hardware design correctly evaluates the sub-function p; formally verifying that an instantiation of the hardware design implements a function that is polynomial of degree k in p by formally verifying that, for all values of p in the set of values of p, an instantiation of the hardware design has a constant kth difference; and verifying that an instantiation of the hardware design generates an expected output in response to each of at least e different values of p in the set of values of p, wherein e is equal to k when a value of the kth difference is predetermined and e is equal to k+1 when the value of the kth difference is not predetermined.