In general, you can. Just remember that you are stacking it N times on a CPU and, depending on the function, there is hardware that can do it more efficiently t

In general, you can. Just remember that you are stacking it N times on a CPU and, depending on the function, there is hardware that can do it more efficiently than a CPU: you're technically inconveniencing yourself more (in comparison to a hacker) by using a cheap function. You're going to gain a lot more by using a function built for high computational cost from the outset. Furthermore, > It can be shown that the repeated hashing reduces the space of possible values, but should reach an inner "cycle" of size roughly sqrt(N) if the hash output values are in a space of size N[1] Using the correct type of function just makes more sense. [1]: http://security.stackexchange.com/a/23308 http://security.stackexchange.com/a/23308