  Post mortem analysis of fracture surfaces of ductile and brittle materials on
the $\mu$m-mm and the nm scales respectively, reveal self affine graphs with an
anomalous scaling exponent $\zeta\approx 0.8$. Attempts to use elasticity
theory to explain this result failed, yielding exponent $\zeta\approx 0.5$ up
to logarithms. We show that when the cracks propagate via plastic void
formations in front of the tip, followed by void coalescence, the voids
positions are positively correlated to yield exponents higher than 0.5.
