The wikipedia article states it as f(x)=f(y) if and only if y is either x xor c _or_ equal to x. So it seems you're right. https://en.wikipedia.org/wiki/Simon%

The wikipedia article states it as f(x)=f(y) if and only if y is either x xor c _or_ equal to x. So it seems you're right. https://en.wikipedia.org/wiki/Simon%27s_problem https://en.wikipedia.org/wiki/Simon%27s_problem