Ask HN: Exact Length of Bezier Curve

I am trying to find the length of a cubic Bezier curve. I'll be targeting c#, but a solution in any language will do (I'll translate). Here's the catch; I need a solution that is not an approximation (does not include steps or tolerance). I'll be using it in a space where precision is important.

I've found references to an algorithm like this existing (a very old one); but every link to it is dead.

Does anyone have experience with this problem?