@mttaggart The article claims that factorisation takes exponential time, I.e., is proportional to e^(an) where a is a constant and n is the number of bits in the number to be factored. But that's not true: the best factoring algorithm known to date, the General Number Field Sieve, takes subexponential time. This class of functions grows faster than any polynomial, but slower than any exponential. One example of a subexponenrial function is e^(√n).