What is blindness and forgeability in Chaum's blind signature scheme?
It (Blind Signature) is unconditionally blind, because if you take a blind message $m\cdot r^e$ and then sign it, you get $m^d \cdot r$ which distributes like a random element in a subgroup of $Z^{*}_{N}$ so even if you have unlimited computational power you can't extract $m^d$ from looking at $r \cdot m^d$. Even if you factor $r \cdot m^d$ you won't know for sure which parts belong to $r$ and which to $m^d$.

However if you have infinite computational power you can just find $d$ from $(N, e)$, hence it is conditionally (computationally) un-forgable.